Here's everything we know about the Waffle House massacre in Tennessee

Four people were murdered and at least seven others were injured when a gunman opened fire inside a Tennessee Waffle House early Sunday morning, according to the Tennessean.

Here's everything we know:

• The killing began around 3:23 a.m. CST in Antioch, a town south of Nashville.
• The killer used an "assault-style" weapon, according to police.
• The killer exited his vehicle, where he immediately murdered two people outside the Waffle House. He then entered the Waffle House and continued to fire, where he murdered two more people and wounded numerous others.
• The shooting only ceased thanks to the heroics of one diner, who hid in the restaurant's bathroom and monitored the killer. Once he saw the opportunity, he sprung into action and rushed the murderer. The man was able to wrestle the gun away, causing the murderer the flee the scene.
• Police identified the killer as a 29-year-old man from Illinois who lived in an apartment complex near the restaurant. He was reportedly naked when he opened fire in the restaurant. He remains at-large.
• So far the motive for the shooting appears to be random, CNN reported.

Here's the at-large shooter:

Police last said the suspected killer was seen wearing pants and no shirt. They have drafted warrants for him, presumably to search his vehicle and home.

What did police say?

"Keep your doors locked, keep your eyes open. If you see this individual — if you see a nude guy walking around this morning — call the police department immediately," Metro Nashville police spokesman Don Aaron said, according to CNN.

Regarding the heroic customer who engaged the shooter, Aaron said there is "no doubt he saved many lives by wrestling the gun away and then tossing it over the counter, and prompting the man to leave."

Did police already know of the suspect?

Unfortunately, yes, according to the Tennessean. Aaron said federal and local investigators were aware of him "due to previous interactions."