Neighbors and others described David Katz, the gunman who shot up a video game tournament on Sunday, killing two people and injuring 11 before turning the gun on himself, as someone who kept to himself.

Katz, 24, is suspected of going on a shooting rampage in the northern Florida city of Jacksonville.

Sheriff Mike Williams said final confirmation of the suspect’s identity was pending as the FBI in Baltimore aided in the investigation.

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A crime reporter for the Baltimore Sun tweeted that court records relating to the divorce of Katz’s parents say that he had “significant medical problems and healthcare needs.”

According to Business Insider, announcers at a 2017 tournament said that Katz was not showing “much emotion” while playing his games.

“David Katz keeps to himself. He’s a man of business,” the announcer said. “He’s not here to make friends.”

“You can’t even get him to open up about anything, it’s like pulling teeth,” he added.

VIDEO | Steve Tasker interviews David Katz (Bread), the suspect in today's mass shooting at the Jackonville Landing, at a 2017 Madden competition in Buffalo. https://t.co/UcHQIWMfIA — Florida Times-Union (@jaxdotcom) August 27, 2018

According to an eyewitness who spoke to the LA Times, Katz opened fire at the tournament after having been eliminated earlier in the day.

Another eyewitness told Action News Jax that Katz, known as “Bread” online, had been acting strangely before the shooting.

“He had shades on. He didn’t speak to anybody. After we played, I went to shake his hand and tell him good game and he just looked at me and didn’t say anything,” the witness said.

Katz was reportedly Jewish.

On Sunday evening, the FBI said, its agents searched a family home of the man authorities believed was behind the attack. Photographs from the scene of the raid appeared to show a mezuzah attached to the doorframe.

Jewish religious law and customs require that mezuzahs be affixed to door frames on the portal’s external frame.

Heavily armed agents, some in bulletproof vests and brandishing long guns, could be seen entering an upscale townhome complex near Baltimore’s Inner Harbor.

An FBI spokesman, Dave Fitz, confirmed that agents had gone to the house of Katz’s father in Baltimore. He declined to release specifics, citing the ongoing investigation. T.J. Smith, chief spokesman for the Baltimore Police Department, also said that the agency was assisting law enforcement partners “with some information that has led authorities to Baltimore.”

A neighbor said that Katz and his father were unassuming.

“There’s nothing remarkable about them,” said a neighbor. “There’s not anything suspicious about them at all. We have lived here for a long time and we never talk to them.”

A reporter for WBAL-TV in Baltimore said that according to Maryland court records, Katz’s parents were divorced in 2007 and that at the time, his father worked for NASA and his mother for the FDA.

At the tournament, eyewitnesses Marquis Williams and Taylor Poindexter at first thought they heard a balloon popping. When the loud bangs kept coming, the Chicago couple and fellow video gamers attending a weekend tournament recognized them as gunfire and began scrambling for an exit.

As he fled, Williams, 28, said, he could see the back of the gunman’s head as the attacker appeared to be walking backward as he fired.

“We didn’t see like a face,” Poindexter, 26, told reporters a few hours after the attack, standing on crutches after spraining her ankle trying to escape. “We did see him with two hands on a gun, walking back just popping rounds.”

The couple said people trampled others in the panic to escape. They ran to a nearby restaurant, where workers were waving people inside, and hid in a bathroom until police arrived.

The deadly violence stunned gamers competing Sunday in Jacksonville during a “Madden NFL 19” video game tournament. Jacksonville Sheriff Mike Williams said the gunman killed two people and shot nine others before fatally shooting himself.

Madden is a hugely popular multi-player video game based on the National Football League, which in a statement said it was “shocked and deeply saddened by the horrific tragedy.”

The tournament at The Landing entertainment and shopping complex — a regional qualifier for finals in Las Vegas with a $25,000 prize — took place at the GLHF Game Bar.

The competition was held in a gaming bar that shares space with a pizzeria. Viewers could watch the games online and see the players.

“No one deserves to die over playing a videogame, you know?” said “Madden” competitor Derek Jones, 30, of Santa Fe, New Mexico. “We’re just out here trying to win some money for our families and stuff.”

Jones said he was sitting in a back patio outside the tournament venue when he heard the gunshots Sunday. He jumped a fence and ran, leaving behind his backpack and cellphone.

“You know, I’m glad I lost today,” Jones said. “Because if I’d won, I would have been in that game bar right then playing a game and not paying attention. And he could have come and I’d probably be dead right now.”

Another player, “DubDotDUBBY,” said a bullet had grazed his head.

“I feel fine, just a scratch on my head. Traumatized and devastated,” he tweeted.

Jones said he knew Katz by the gamer tags he used online — often “Bread” or “Sliced Bread” — and had played against him online but had never spoken to him personally.

In 2017, Katz won a similar tournament in Buffalo.

Congrats to David Katz, the Madden 17 Bills Championship winner! Thanks for following along, Bills fans. https://t.co/YHJHzlFElc pic.twitter.com/incdEhLxkT — Buffalo Bills (@buffalobills) February 27, 2017

Nine other people wounded by the gunfire were all in stable condition Sunday evening after being taken to hospitals, Williams said. He added that two others were injured in the rush to flee the gunfire.

Investigators were looking into an online video that appeared to capture the scene right before the shooting began, Williams said. A red dot that appears to be a laser pointer is visible on the chest of a player seconds before the first of about a dozen gunshots rings out.

WARNING: Video contains graphic content

Multiple people have been killed after a shooting at a video game tournament Sunday in Jacksonville, Florida. Here is what we know so far https://t.co/Y63aZrlbOY pic.twitter.com/QbBB4ORwfL — CBS News (@CBSNews) August 26, 2018

Jason Lake, the founder and CEO of compLexity, a company that owns professional esports teams, said on Twitter that one of his players, 19-year-old Drini Gjoka, was shot in the thumb.

Gjoka tweeted: “The tourney just got shot up. Im leavinng and never coming back.” Then: “I am literally so lucky. The bullet hit my thumb. Worst day of my life.”

In Washington, White House spokeswoman Sarah Huckabee Sanders said President Donald Trump had been briefed on the attack and the White House was monitoring the situation.

The Jacksonville Landing, in the heart of the city’s downtown, also hosts concerts and other entertainment. It was the site of a Trump rally in 2015, early in his campaign for the White House.

Marquis Williams said the shooting rampage was another tragic sign that elected officials should take action to curb gun violence.

“Politicians, wake up because the people you’re supposed to representing are dying,” Williams said. “Quit sitting on your butts. Quit collecting checks and do something.”

Survivors of February’s high school shooting in Parkland, Florida, expressed sorrow at news of another mass shooting in the state.

“Once again, my heart hurts and all of me is so angry. We cannot accept this as our reality,” said Delaney Tarr, one of the organizers of the student-led March for Our Lives movement.

Florida has suffered multiple shootings in recent years: 49 were killed in a June 2016 attack on a gay nightclub, while 17 were killed at Marjory Stoneman Douglas High School earlier this year.