Calif. Mass Shooter ID'd as Marine Corps Vet, 28, Who Had Disturbing Episode Only Months Earlier

The gunman who opened fire late Wednesday night at a Southern California bar, killing 12 people, has been identified as 28-year-old Ian David Long, a veteran of the Marine Corps with a history of volatile behavior, PEOPLE confirms.

Long was identified by Ventura County Sheriff Geoff Dean at a Thursday morning news conference. Dean previously said that authorities believe the shooter acted alone when he attacked the Borderline Bar & Grill late Wednesday in Thousand Oaks.

Later Thursday, Dean described the shooter as having a history of run-ins with law enforcement — both notable and minor — including in April, when authorities were called to the home he had shared with his mom for many years.

“He was somewhat irate and acting a little irrationally,” Dean said. A mental health specialist was called and responding deputies believed that the shooter may have been suffering from symptoms related to PTSD.

However, Dean said, authorities did not feel then that he could be involuntarily taken into psychiatric custody (also known as a 5150, in reference to state law).

The shooter’s longtime neighbor Donald J. McCloud tells PEOPLE he was long known for his aggressive nature.

“He was always arguing,” says McCloud, 79. “We could hear him sitting right there screaming and shouting. … He had flood lights in the backyard. Sometimes at 3 o’clock in the morning, he had the flood lights on.”

McCloud says there was “peace and quiet” while the shooter was deployed — and which lasted exactly until he came back.

“She [the shooter’s mom] was intimidated, I think, by him,” McCloud says. “I can understand that. He was a strong guy, he was in the military. He was bigger than she is. And it’s very difficult. Unfortunately he didn’t get any help.”

Speaking with reporters on Thursday, Sheriff Dean said the gunman’s history also included two traffic incidents, a citation and a collision, as well as being the victim of a battery at another local bar in 2015.

According to a Marine Corps spokesman, the shooter served from 2008 to 2013 and was deployed for six months in Afghanistan, from November 2010 to June 2011. He was last assigned to Hawaii and left the Marines with the rank of corporal. He was honorably discharged, PEOPLE confirms.

He appears not to have received any treatment for PTSD from the Department of Veterans Affairs, according to the VA.

Shots were first reported at about 11:20 p.m. The shooter was found dead along with 11 of his victims after authorities entered the bar soon after. Dean said Thursday that the shooter apparently killed himself.

The shooter was armed with a .45-caliber handgun which he had purchased legally, Dean said. The magazine had been illegally modified with an extended magazine, but it was unclear if he reloaded during the minutes-long shooting.

Witnesses told the New York Times that he was dressed in all-black with a hat and jacket and shot a security guard before opening fire onto the crowd while throwing smoke grenades, causing chaos.

Sheriff Dean said, “He walked up to the scene, he shot the security guard that was standing outside. He stepped inside, it appears that he turned to the right and shot several of the other security and employees there and then began opening fire inside.”

“I saw him shoot,” Teylor Whittler told the Times, adding that someone yelled, “Everybody get down.”

“People started running to the back door,” she continued, saying another person told everyone, “Get out — he’s coming.”

On Thursday, authorities said it was too early to discuss a possible motive. Dean said that while it appeared it was not a totally random attack — “He’s a resident of this area, and common sense would speculate that there’s some reason he went here” — it did not seem that the shooter targeted specific employees.

“The first people he shot point-blank,” witness John Hedge told PEOPLE. “It looked like he was going after those specific people near the front door,” he says. “I saw him shoot the security guard and just thought, What do I do or don’t?”

“I ran to the bathroom to try to go hide, and then I saw a couple people make it out the front door,” Hedge said. “I didn’t think I would be able to escape there, because he was in a 10-foot radius of the front door [and] cash register area.”

The gunman began “making his way around the front desk area,” said Hedge. “It seemed like he had a vendetta against the girls working the front desk.”

The first among the victims to be named was longtime sheriff’s Sgt. Ron Helus.

Helus served for 29 years in the sheriff’s office and was planning to retire soon, according to the Washington Post. He was one of the first responders on the scene and is being hailed a “hero.”

Authorities said he was shot multiple times as he entered the bar and later died at the hospital.

“He went into save lives, to save other people,” Dean said, according to CNN. “He was totally committed, he gave his all, and tonight, as I told his wife, he died a hero.”

On Thursday morning, President Donald Trump tweeted his thanks to the first responders, calling the shooting “terrible.”

The bar was hosting a “College Country Night,” according to the AP and CNN.

The network described Borderline as a popular spot for local college students. On Wednesday evening young adults under 21 were allowed entrance, according to the Times.

“[It’s] just a place you go to hang out with friends,” witness Holden Harrah told CNN. “Just have fun as young adults.”