3:45 PM PT -- An Instagram user just posted video from inside Borderline Bar & Grill during the shooting. In the video you can see a shadowy figure moving around as gunshots ring out -- the IG user claims that figure is Long, and he was firing shots at injured victims at the time.

8:52 AM PT -- According to more dispatch audio -- obtained by TMZ -- officers can be heard communicating Long suffered 3 gunshot wounds to the chest and is down. They describe him as wearing all black with a beard.

8:35 AM PT -- Long served in the U.S. Marine Corps from 2008-13 and was deployed to Afghanistan from 2010-2011, his last duty assignment was in Hawaii. His military occupational specialty was machine gunner.

He was decorated too ... some awards included the Navy Unit Commendation (x2), Navy Meritorious Unit Commendation, Combat Action Ribbon, Marine Corps Good Conduct Medal, Afghanistan Campaign Medal, Global War on Terrorism Service Medal and the National Defense Service Medal.

7:40 AM PT -- President Trump has ordered flags flown at half-staff on all public buildings and military facilities until sundown on Saturday.

6:45 AM PT -- The shooter's been identified as 28-year-old Ian David Long -- a retired Marine who served in Afghanistan.

We found this pic of Long at a cemetery that appears to be in the L.A./Thousand Oaks area. We're told he was heavily tattooed.

A horrific scene unfolded at a bar packed with college students Wednesday night as a gunman opened fire, and at least 12 people are dead.

Borderline Bar & Grill in Thousand Oaks was hosting its weekly College Country Night. College students from the area were enjoying themselves, line dancing when, at around 11:20 PM, shots rang out.

A man dressed in all black began firing a handgun. Several patrons broke windows to allow others to escape, cutting themselves on shards of glass as they exited.

Sheriff's deputies responded quickly and as they rushed the bar the gunman opened fire on them, killing Sergeant Ron Helus.

Long reportedly drove his mother's car to the bar. He threw smoke bombs into the crowd before opening fire.

No word yet on the number of injured, but around a dozen people are known to have gone to the hospital. It appears some may have driven themselves and may not be accounted for yet.

President Trump tweeted, "Great bravery shown by police ... God bless all of the victims and families of the victims. Thank you law enforcement."

We spoke with multiple coaches from Long's high school baseball team who remember him as a sad loner who didn't have many friends. As one coach put it, he had "sad eyes" and never appeared happy. We're told he also wore an army jacket to school often and it was clear he had ambitions to join the military. One coach tells us, "He was a quiet kid. Respectful. But kept to himself."

Story developing ...