This story has been updated.

It’s been 24 hours since the horrific attack at the Washington Navy Yard claimed the lives of 12 Americans. The FBI says Aaron Alexis, an information technology employee with ties to the base, is the individual responsible for the deadly assault.

Details about the now-deceased former Navy reservist who may have been suffering from numerous mental illnesses (including hearing voices in his head) are still forthcoming, as authorities attempt to put together a motive and to better understand what, exactly, unfolded.

As with any breaking news story, information about the incident has been somewhat fluid, with new and conflicting details emerging throughout the ordeal. Hashing through the finer points can be quite complicated, so we’ve put together some of the newest and most important details to provide everything you need to know about what attack.

Here’s What Happened

To begin, the Daily Mail provides an overview of how the incident unfolded:

Gunman Aaron Alexis was shot dead by responding officers after he opened fire inside a Navy facility around 8:20 a.m. on Monday morning, killing 12 people aged 46-73.

 [...]

Alexis, who worked as a civilian I.T. contractor at the military base in the nation’s capital, entered the cafeteria of Building 197 just before 8:15 a.m. … and began shooting.

While some reports have claimed that Alexis used an AR-15, a shotgun and a handgun, CNN is now reporting that the alleged shooter may not have used an AR-15 after all. CNN reports:

[F]ederal law enforcement sources told CNN Tuesday that authorities have recovered three weapons from the scene of the mass shooting, including one — a shotgun — that investigators believe Alexis brought in to the compound. The other two weapons, which sources say were handguns, may have been taken from guards at the Navy complex.

The sources, who have detailed knowledge of the investigation, cautioned that initial information that an AR-15 was used in the shootings may have been incorrect. It is believed that Alexis had rented an AR-15, but returned it before Monday morning’s shootings. Authorities are still investigating precisely how many weapons Alexis had access to and when.

Washington Navy Yard Shooting Day 2: A Roundup of Everything You Need to Know | Aaron Alexis

In this handout photo provided by the FBI, Aaron Alexis is shown in a photo prior to the mass shooting at the Washington Navy Yard on September 16, 2013 in Washington, D.C. Credit: Getty Images

While initial reports claimed that Alexis likely gained access to the Washington Navy Yard with someone else’s pass, this detail has now come under scrutiny. In a report last night, TheBlaze highlighted that, based on the FBI’s own account, the alleged shooter had “legitimate access” to the base:

At the time of the rampage, suspected shooter Aaron Alexis was an information technology employee with The Experts, a company that was a Defense Department subcontractor on a Marine computer project, authorities said.

Valerie Parlave, head of the FBI’s field office in Washington, said he had legitimate access to the base as a defense contractor and used a valid pass.

Alexis had been a full-time Navy reservist from 2007 to early 2011, leaving as a petty officer third class, the Navy said. It did not say why he left. He had been an aviation electrician’s mate with a unit in Fort Worth.

Previously, the New York Daily News reported:

The ID of retired Navy Chief Petty Officer Rollie Chance was found near Alexis’ body in Building 197. FBI agents later questioned Chance at his Virginia home. But Alexis may have had a security clearance of his own. He worked for The Experts Inc., part of Hewlett-Packard Co., and the Navy subcontractor’s CEO, Thomas Hoshko, told Reuters that the gunman had a “secret clearance” and was scheduled, starting this month, to work out of the Navy Yard with a military-issued ID card. Hoshko said it was “not clear” if Alexis’ assignment was to start Monday.

Washington Navy Yard Shooting Day 2: A Roundup of Everything You Need to Know | Aaron Alexis

This undated cell phone photo provided by Kristi Kinard Suthamtewakul shows a smiling Aaron Alexis in Fort Worth, Texas. The FBI has identified Alexis, 34, as the gunman in the Monday, Sept. 16, 2013 shooting rampage at at the Washington Navy Yard in Washington that left thirteen dead, including himself. Credit: AP

Some are beginning to question whether security was lax at the base. On Monday, one security expert told WOI-TV that the tragedy likely could have been avoided and that security at the base was potentially impacted by budget cuts:

The security expert and Senior Navy Officer we talked to said he’s been to that naval yard many times.  And he thinks recent budget cuts and a lack of security are to blame.

It’s important to note the comments he gave us are based on the few facts known as of Monday night about the shooting.

“We don’t have enough Navy cops there,” Tom Conley said.

He said that’s what it all boils down to.  He said this tragedy that hit the heart of our country and killed innocent people could have been avoided.

The Shooter Acted Alone

To clear up some confusion based on past reports, it is now believed that Alexis acted alone. When the story first broke, police and media spoke of additional shooters, but authorities now claim this was unfounded.

The AP has more about some of the confusion that initially colored the investigation:

In the confusion, police said around midday that they were searching for two accomplices who may have taken part in the attack – one carrying a handgun and wearing a tan Navy-style uniform and a beret, the other armed with a long gun and wearing an olive-green uniform. Police said it was unclear if the men were members of the military.

“We do now feel comfortable that we have the single and sole person responsible for the loss of life inside the base today,” Washington police Chief Cathy Lanier told the AP.

The Motive

There is no definitive motive yet, but there are some theories floating around. The Daily Mail explains:

No motive has been revealed for Monday’s shooting, but speculation is growing his dismissal from the U.S. Navy for ‘misconduct’ in January 2011 may have inspired him to commit deadly revenge.

The Pentagon confirmed that he was awarded the Global War on Terrorism Service Medal and the National Defense Service Medal prior to his discharge in January 2011. [...]

Despite the lack of an acknowledged motive, one U.S. official has been quoted as saying Alexis was discharged from the Navy in 2011 following a series of incidents of ‘misconduct.’

And CBS News adds: “He then spent four years working as an aviation electrician’s mate, most recently at the naval air station in Fort Worth, Texas. Military records show ‘a pattern of misconduct,’ and in January 2011 Alexis received a general discharge.”

Of course, there’s also a key detail that TheBlaze reported on last night — one that might have contributed to alleged shooter’s violent streak: Alexis’ apparent fascination with violent video games:

Chris Childs, director of TheBlaze TV’s “The Pat & Stu Show,” told us he frequently visited the Thai restaurant Alexis worked at in Fort Worth, and got to know him over time.

“The thing that really struck me was the fact that he was really big into the shooter video games,” Childs told TheBlaze. “We would talk about all kinds of stuff… I know the family that owns the Thai restaurant is devastated because they can’t imagine that he would do this. I can’t imagine it.”

Childs also said Alexis seemed like an “extremely normal guy.” He said the deceased shooter also spoke about his “out of the blue” visit to Thailand.

Washington Navy Yard Shooting Day 2: A Roundup of Everything You Need to Know | Aaron Alexis

Television reporters do stand-ups at 3rd Street and M Street, SE, near the Navy Yard shootings on September 16, 2013 in Washington, DC. A US naval reservist launched out a shooting rampage on a base in the heart of Washington on Monday, killing 13 people and exchanging fire with police before losing his own life. Credit: AFP/Getty Images

The Telegraph sheds more light upon this purported penchant for violence:

The addiction to violent video games and guns was at odds with his devout commitment to Buddhism, which saw Alexis spending half the day every Sunday meditating at the Wat Busayadhammvanaram temple in Fort Worth, Texas over a period of several years. He also spent a month in Thailand in April, The Daily Telegraph can disclose. [...]

The darker side to Alexis’s character saw him playing violent “zombie” video games in his room, sometimes from 12.30pm until 4.30am.

Mr Suthamtewakul said: “He could be in the game all day and all night. I think games might be what pushed him that way. He always had this fear people would steal his stuff so that’s why he would carry his gun all the time. He would carry it when he was helping out in the restaurant which scared my customers.”

It’s a complex picture to paint, but the AP provides some details about Alexis’ alleged character that are worth noting: “He was described as a Buddhist who had also had flares of rage, complained about the Navy and being a victim of discrimination and had several run-ins with law enforcement, including two shootings.”

Whether these issues play into his reasoning remains to be seen.

Suffering From Mental Illness?

Officials now claim that Alexis may have been suffering from a host of mental illness, including a sleep disorder and paranoia. But perhaps most notably, the alleged shooter was also apparently hearing voices in his head — and he was reportedly receiving treatment for these serious issues. The AP explains:

Aaron Alexis, 34, had been treated since August by the Veterans Administration for his mental problems, the officials said. They spoke on condition of anonymity because the criminal investigation in the case was continuing. The Navy had not declared him mentally unfit, which would have rescinded a security clearance that Alexis had from his earlier time in the Navy Reserves.

Family members told investigators that Alexis was being treated for his mental issues.

Past Legal and Anger Issues

As TheBlaze previously reported, this isn’t the first time Alexis has clashed with authorities, as he has somewhat of a complicated past with police:

On May 6, 2004, two construction workers saw Alexis “pull a gun from his waistband and fire three shots into the two rear tires of their Honda,” according to Seattle Police. The workers apparently told police he had been upset over the parking situation nearby and had “stared” construction workers down every day over the past month.

Alexis told police he had been “mocked” by the workers and had an anger-fueld “blackout.” Seattle Police also say he told them he was present during the 9/11 terrorist attacks and explained “how those events had disturbed him.”

Seattle detectives talked to Alexis’ father, who said he suffered from anger management problems associated with PTSD.

Alexis was also arrested in September 2010 for accidentally discharging a firearm, according to a police report obtained by KXAS-TV. However, the documents reportedly indicate he was never officially charged.

The police report reveals that a woman called police in September 2010 after she heard a “loud pop” and saw a “hole in her floor.”

Police then interviewed Alexis who said that “he did have a gun” and claimed to be “cleaning it when it went off.” A gun cleaning kit was found near the firearm.

“After investigating the situation, Aaron was taken to 350 W. Belknap and booked,” the police report concludes.

And as Daily Mail reported, there also may be an additional disorderly conduct charge, for which Alexis purportedly spent two nights in jail in DeKalb County, Ga. There are few details about this alleged incident.

Washington Navy Yard Shooting Day 2: A Roundup of Everything You Need to Know | Aaron Alexis

This undated cell phone photo provided by Kristi Kinard Suthamtewakul shows Aaron Alexis in Fort Worth, Texas. The FBI has identified Alexis, 34, as the gunman in the Monday, Sept. 16, 2013 shooting rampage at the Washington Navy Yard in Washington that left thirteen dead, including himself. Credit: AP

The Victims

On Monday evening, police released a partial list of the victims. TheBlaze subsequently published the names and ages of seven of the 12 who were killed during the violence rampage. Here is that list: 59-year-old Michael Arnold, 53-year-old Sylvia Frasier, 62-year-old Kathy Gaarde, 73-year-old John Roger Johnson, 50-year-old Frank Kohler, 46-year-old Kenneth Bernard Proctor and 61-year-old Vishnu Pandit.

The Associated Press assembled biographies on some of the victims as well. Among them, the outlet noted that Arnold, from Lorton, Va., was a Navy veteran and a pilot. Here’s more about his background:

Arnold graduated from the United States Naval Academy in Annapolis, Md., and served in the Navy for 29 years, before retiring as a captain last October, according to an article in the Navy Supply Corps Newsletter. Arnold, who had two master’s degrees from the University of Washington in Seattle, then went to work for LMI, a consulting firm based in McLean, Va.

[According to his uncle, he] worked at the Navy Yard on a team that designed vessels such as the USS Makin Island, a Wasp-class amphibious assault ship used by the Marine Corps. Jeff Bennett, a vice president at LMI, told The Washington Post that Arnold “was just a solid, solid citizen … great American.”

And of Gaarde, from Woodbridge, Va., the AP noted that she was a financial analyst. Her husband, Douglass, declined to speak out following her death, but he did write a brief note in an e-mail to the outlet that he is understandably struggling following the tragic loss. The AP has more:

“Today my life partner of 42 years (38 of them married) was taken from me, my grown son and daughter, and friends,” he wrote. “We were just starting to plan our retirement activities and now none of that matters. It hasn’t fully sunk in yet but I know I already dearly miss her.”

Madelyn Gaarde, of Grand Junction, Colo., who’s married to Douglass Gaarde’s brother, said her sister- and brother-in-law met while he was studying electrical engineering at the University of South Florida in Tampa.

Douglass Gaarde, an Illinois native, also worked for the Navy until his retirement last year, his sister-in-law said.

“She was a very gracious person and very welcoming,” she said of Kathleen Gaarde.

You can read more about the victims’ biographies here.

In addition to the 12 lives that were taken, eight others were injured in the shooting rampage. A police officer and two female civilians were shot, but all three are expected to survive, according to the AP.

Alexis was born in Queens, New York in 1979. Friends and acquaintances were surprised by his actions, although it has been widely reported that he allegedly had anger management problems.

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