This story was updated Feb. 16 at 11:05 a.m. ET with new information from authorities about Nikolas Cruz's link to a white nationalist group in Florida.
More details are emerging about Nikolas Cruz, the suspect who is accused of having opened fire on students at a Florida high school Wednesday that left 17 dead and 15 more injured.
The 19-year-old has been identified by authorities as the man who was wearing a gas mask and carrying smoke grenades when he walked into Marjory Stoneman Douglas High School in Parkland shortly after 2 p.m. local time. He started shooting randomly at students, creating horror, and leaving a bloodbath in his wake.
Officials are now scouring the suspected killer's social media accounts, cellphone, talking to those who know him, and searching the home where he has lived since late November.
Broward County Sheriff Scott Israel has described some of the things they have discovered as "very, very disturbing."
Douglas High School officials expelled Cruz from the school for disciplinary reasons last year, Israel said during a news conference.
Additionally, the AP is reporting that a white nationalist group in Florida is claiming that Cruz was a member of their organization. This claim has not yet been independently verified.
Update: Authorities in Leon County told the Tallahassee Democrat that they were unable to find any information linking Cruz to the Republic of Florida Militia. The group's self-proclaimed leader, Jordan Jereb, had made the claim that was first reported by The Associated Press and later by numerous news organizations.
The Latest: The leader of a white nationalist militia says Florida school shooting suspect Nikolas Cruz was a membe… https://t.co/wcyfe3ps34— The Associated Press (@The Associated Press)1518717543.0
Where were his parents?
Cruz's parents adopted him and a younger brother as infants. Their father died 10 years ago from a heart attack. Their mother, Lynda, died from complications of the flu in November. She was 68.
The alleged shooter was taken in by a family after his mother died.
Jim Lewis, a lawyer for the family, told CBS they noticed signs of depression, which he said would be expected after losing his mother a few months ago.
But they didn't see any alarming signs of aggression or any other indications that Cruz would be capable of such violence.
He had an AR-15 that was locked in a gun safe at the home.
The family is "grief-stricken" and "in shock," Lewis said.
What did other students say about Cruz?
Students told local news outlets that Cruz was a loner and they knew "he would be the one to shoot up the school."
"He always just seemed very quiet and strange," said Brandon Minoff, a senior who worked on a group project with Cruz as a sophomore.
"He told me how he got kicked out of two private schools. He was held back twice. He had aspirations to join the military. He enjoyed hunting," Minoff said.
Dakota Mutchler, 17, a former close friend of the Cruz, told Fox News that some of the shooting suspect's Instagram posts were about killing animals and doing target practice in his backyard with a pellet gun.
He had not seen Cruz since being expelled, Mutchler added.
Another former classmate, Chad Williams, a senior, told Reuters that he remember Cruz being troubled in middle school.
In eighth grade, the school expelled Cruz for repeatedly setting off the fire alarm at school, Williams said.
Williams recently saw Cruz carrying several gun publications at the high school. He thought Cruz was there to pick up his younger brother.
“He was crazy about guns,” Williams said. “He was kind of an outcast. He didn’t have many friends. He would do anything crazy for a laugh, but he was trouble.”
What did he post on his social media accounts?
Cruz posted alarming comments and photos on various social media sites. His accounts have been suspended, police said.
Alleged Florida shooter appeared to flaunt weapons on Instagram https://t.co/IrVwsGgBRU https://t.co/PKrArFFgpt— New York Post (@New York Post)1518669454.0
He also made disturbing comments on videos including, "I whana shoot people with my AR-15," "I wanna die Fighting killing s**t ton of people," and "I am going to kill law enforcement one day they go after the good people."
Ben Bennight posted a video on YouTube that a user named Nikolas Cruz commented on last September.
“I’m going to be a professional school shooter,” Cruz wrote.
Bennight told Buzzfeed News that he alerted YouTube and took a screenshot of Cruz's comment to the FBI.
He said agents responded quickly.
"They came to my office the next morning and asked me if I knew anything about the person," Bennight added. "I didn't. They took a copy of the screenshot and that was the last I heard from them."
"In 2017, the FBI received information about a comment made on a YouTube channel. The comment simply said, 'I'm goi… https://t.co/rn6RQJabaZ— CBS News (@CBS News)1518710307.0
"The FBI conducted database reviews and other checks, but was unable to further identify the person who posted the comment," FBI Special Agent in Charge Robert Lasky said Thursday during a news conference.
Early Thursday morning, Bennight was contacted again.
FBI agent Ryan Furr left Bennight a voicemail, " "I think we spoke with you in the past about a complaint that you made about someone making a comment on your YouTube channel."
"I just wanted to follow up with you on that and ask you a question with something that's come up, if you wouldn't mind giving me a ring," Furr said in the message.
Officials have not confirmed whether the YouTube user was the same Nikolas Cruz from Wednesday's massacre, but the YouTube account was shut down for violating the site's policy on violence.
Authorities charged Cruz with 17 counts of premeditated murder.
Police booked him in the county jail in Fort Lauderdale after several hours of questioning.
Cruz was arraigned in court on Thursday and the judge denied bond.