Thousand Oaks, CA – Authorities have identified the gunman who murdered 12 people inside of a local bar Wednesday night, and the heroes who died saving people.

At approximately 11:20 p.m. on Wednesday night, 28-year-old Ian David Long headed over to the Borderline Bar & Grill, where several hundred people were enjoying “college country night,” Ventura County Sheriff Geoff Dean told NBC News.

Armed with a .45-caliber Glock handgun and dressed in black, the hooded gunman first shot the security guard outside.

He then walked into the bar, “turned to the right, shot several other security and employees and began opening fire inside the nightclub,” Sheriff Dean said.

According to witnesses, patrons inside the bar mostly fell silent and fled to various corners of the building, attempting to hide, CNN reported.

“He didn’t say anything, at least not that we could hear, witness Matthew Estron told NBC News. “Everyone was just trying to get out.”

Others tossed stools through windows and hoisted people out, saving dozens of lives, CNN reported.

Ventura County Sheriff’s Sergeant Ron Helus, a 29-year veteran of the force, was among the first law enforcement officers to respond to the scene, Sheriff Dean said told CBS News early Thursday morning.

Just before he went into the bar, the sergeant wrapped up a phone call with his wife.

“I gotta go,” he told her, according to the sheriff. “I love you. Call you later.”

“When he heard gunfire, he went in and that’s something [we] would expect from Ron,” he said, according to KCBS.

“He was willing to sacrifice his life for the sake of others,” the sheriff noted, according to NBC News. “He ran into danger — he didn’t walk.”

He was shot multiple times after he entered the building, and was later pulled out of the line of fire by a California Highway Patrol trooper, CBS News reported.

The 54-year-old sergeant was rushed to a local hospital, where he died at approximately 2 a.m. on Thursday.

Additional officers, including FBI agents and a SWAT team, arrived at the scene a short while later and made their way into the bar, NBC News reported.

Bodies littered the floor, while survivors huddled in terror or tried desperately to escape.

“They found people hiding in restrooms, people hiding in attics,” Sheriff Dean said.

Long was later found dead inside the bar with an apparent self-inflicted gunshot wound, USA Today reported.

“When the officers made entry, the suspect was already deceased,” Sheriff Dean said during the press conference. “There are 11 victims. I will not count the suspect as a victim.”

“It’s a horrific scene in there,” Sheriff Dean said. “There is blood everywhere.”

“This is, by far, the most horrific thing I’ve seen in my 41 years,” he told NBC News.

Some witnesses said Long detonated smoke bombs inside the bar before he opened fire, but police have not confirmed those accounts.

Investigators recovered Long’s weapon, which was equipped with an extended magazine that is illegal in the state of California, according to USA Today.

According to the sheriff, investigators “have no idea what the motive is at this point,” NBC News reported.

In the midst of the carnage and terror Long unleashed, heroic leaders and protectors emerged.

Borderline Bar & Grill bouncer and promoter Justin Meek, 23, was off duty on Wednesday night, so he went to the club with his friends to have a good time, KSWB reported.

When Long opened fire, Meek was among the first people to jump into action.

He broke windows to usher people out of the bar to safety, rescuing many before he was fatally shot by the gunman.

“Meek heroically saved lives in the incident,” a spokesperson for his alma mater, California State University, told KSWB. “Cal Lutheran wraps its arms around the Meek family and other families, and around every member of this community of caring.”

Shooting survivor Matt Wennerstrom used a barstool to smash out a window, then helped dozens of people to escape, KABC reported.

“We probably pushed 30 or 35 people through that window,” Wennerstrom told the news outlet as he stood outside the bar in a bloody shirt.

“All I did was grab as many people as I could and pull them underneath the table until I heard a break in the shots, and then we got people out of there, as much as we could,” he said.

Six unarmed, off-duty police officers had also been socializing at the bar when the gunfire broke out, NBC News reported.

“I’ve already spoken to a parent who said, ‘They stood in front of my daughter,'” Sheriff Dean told the news outlet. “It was amazing.”

Between 10 and 12 victims suffered injuries of varying degrees, but additional victims with more minor injuries also took themselves to the hospital for treatment.

Eleven people with gunshot wounds or lacerations were treated at the Los Robles Regional Medical Center, and ten have been released.

The eleventh victim was Sgt. Helus.

Grieving father Jason Coffman said that his son, 22-year-old Cody Coffman, was among those murdered by Long, NBC News reported.

“I talked to him last night before he headed out the door,” Jason told reporters through his tears. “First thing I said was please don’t drink and drive. Last thing I said was, ‘Son, I love you.’ That was the last thing I said.”

Alaina Housley, 18, was also among those murdered during the attack, according to her aunt, “Sister, Sister” star and “The Real” host Tamera Mowry-Housley.

“She was an incredible, beautiful girl who didn’t hurt anybody, and was excited to go to Italy for a program overseas,” Mowry-Housley said, according to USA Today.

Housley, who recently graduated from high school with honors, was a freshman at Pepperdine University.

Her family began searching for her as news of the mass shooting broke.

“Her Apple Watch and iPhone still showed her location on the dance floor,” her uncle told the Los Angeles Times.

Long was a U.S. Marine Corps gunner and decorated war veteran who served seven months in Afghanistan.

During his nearly five years of service, he achieved the rank of corporal.

The U.S. Marine Corps released a statement confirming that Long served from August of 2008 until March of 2013, CBS News reported.

He received many commendations for his service, including a Global War on Terrorism service medal, a Navy unit commendation, a combat action ribbon, and an Afghanistan campaign medal.

The Marine Corp extended its condolences to the families of the victims, and called the massacre a “senseless tragedy.”

Sheriff Dean said Long may have been suffering from post-traumatic stress disorder, and that he had a history of minor run-ins with officers in recent years, NBC News reported.

Meanwhile, millions of other people with PTSD have not started murdering people.

Barbara Olasov Rothbaum, a professor in the Department of Psychiatry and Behavioral Sciences and director of the Trauma and Anxiety Recovery Program at Emory University School of Medicine, told USA Today, “This is not PTSD. This is whatever else, what other pathology would cause someone to do this.”

In April, deputies were called to Long’s residence for a report of a disturbance.

They said Long was “acting a little irrationally” and seemed to be “somewhat irate,” but a mental health specialist subsequently determined he could not be held for an involuntary psychiatric evaluation.

Long resided with his mother, Colleen, who was frustrated that her son would not accept help for his mental health struggles, their neighbor, Richard Berge, told USA Today.

His father died of cancer when he was still young, a relative told CBS News.

Berge said that another neighbor told him the walls in Colleen’s home were “full of holes” from being kicked or hit by Long.

“It sounded like he was tearing down the walls of the house,” neighbor Tom Hanson said.

Another neighbor, Tim Tanner, described Long as a “quiet, normal guy” who “kept to himself.”

But Long’s former roommate, Blake Winnett, described him as a loner who was often holed up in his room.

“He was kind of weird, he always locked himself in his room, he was always by himself,” Winnett said, according to USA Today. “I didn’t really know him very well.”