A gunman opened fire in a crowded Southern California bar popular with college students, killing 12 people, including a sheriff’s deputy, police said on Thursday.

The gunman, identified by authorities as Ian David Long, 28, was also found dead on Wednesday night in the office of the Borderline Bar and Grill, located in Thousand Oaks, a suburb about 40 miles from Los Angeles, apparently having shot himself.

Ventura County Sheriff Geoff Dean told a news conference on Thursday morning that Long was a Marine Corps veteran and had apparently fired at random with a .45-caliber Glock handgun with an extra-capacity magazine. There was no known motive.

“Obviously he had something going on in his head that would cause him to do something like this,” Dean said. “Obviously he had some sort of issues.”

He said authorities were obtaining a search warrant for Long’s home.

The Borderline is popular with university students and on Wednesday night was hosting College Country Night. California Lutheran University, located about 5 miles from the bar, canceled Thursday’s classes while Pepperdine University, about 20 miles away, planned a prayer service.

One of the victims was Sheriff’s Sergeant Ron Helus, a 29-year veteran of the department who died at a hospital, Dean said. Helus and a California Highway Patrol officer were the first to arrive at the bar and went inside just before 11:30 p.m. PST (0730 GMT).

A statement from the sheriff’s office said there would be a procession in honor of Helus, who leaves behind a wife and son, on Thursday morning. “Ron’s selfless, heroic actions will never be forgotten,” the statement read.

SCENE LIKE “HELL”

Asked what the scene inside the bar was like, Dean said, “Like ... hell.” Earlier he had described it as “a horrific scene in there. There is blood everywhere and the suspect is part of that.”

Long first shot a security guard outside the bar, stepped inside and resumed shooting, Dean said. Witnesses said Long had used smoke bombs to create confusion but Dean said that had not been confirmed.

Dean, speaking on his last day before retirement, said he had been told 150 to 200 people were in the Borderline at the time and that “it could have been much, much worse.”

Dean estimated 10 to 15 people, including one with a gunshot wound, had gone to hospitals. He said he thought their injuries were minor, and that most of them were likely injured as they escaped, some by breaking windows.

Dean told reporters that officers had gone to Long’s home in April in response to a disturbance call and had found him to be agitated. Mental health specialists talked with Long and determined that no further action was necessary.

Family members of possible victims or survivors of the shooting gathered at a teen center in Thousand Oaks for news of loved ones. A visibly distraught man was seen entering the building.

President Donald Trump, who has resisted a surge in calls for tougher gun controls since 17 students were shot dead at Stoneman Douglas High School in Florida earlier this year, ordered flags to be flown at half-staff at public buildings and grounds.

The Borderline massacre was the fourth mass shooting in the United States in less than two weeks. The others included two women killed at a yoga class in Tallahassee, Florida, two people shot at a grocery in Jeffersontown, Kentucky, and 11 worshippers at a synagogue in Pittsburgh killed by a man shouting “All Jews must die.”

Jerry Nadler, the top Democrat on the House Judiciary Committee, said lawmakers would get to work on legislation including universal background checks when the House of Representatives convenes in January with a Democratic majority.

“We must find a way to stop the senseless, and many times preventable killings that are robbing our country of innocent lives,” he said on Twitter.

“CAN HAPPEN ANYWHERE”

Thousand Oaks, a leafy, sprawling suburb, was named the third-safest city in the United States for 2018 by the website Niche.

“I’ve learned it doesn’t matter what community you’re in,” Dean told reporters when asked if he was surprised this happened in Thousand Oaks. “It doesn’t matter how safe your community is. It can happen anywhere.”

Tristan Appleby, who was at the bar, told CNN that the shooter was dressed all in black and had fired off about a dozen shots, including at those already wounded and lying on the floor.

Witness Taylor Von Molt, 21, who said she was a promoter at the bar, said the gunman wore a black mask with a bandana covering the bottom of his face, and a black hooded sweatshirt.

“I heard what I thought was a balloon pop,” she told CNN. “I was confused because we didn’t have any balloons. I saw him, then I saw him fire his weapon one more time. I ran to the nearest exit and tripped and fell on the way and people kept running on top of me.”

Witness John Hedge told ABC News he was near the front door of the bar when the shooting began.

“I just started hearing these big pops. Pop pop pop,” he said. “There was probably three or four. I hit the ground. I look up. The security guard ... was shot, he was down. The gunman was throwing smoke grenades all over the place. I saw him point to the back at the cash register and he just kept firing.”