A gunman who opened fire at an online video game tournament after losing a match, killing two people then shooting himself, had bragged about being 'one of the better players' at last year's tournament.

David Katz, 24, of Baltimore, carried out the shooting spree with a handgun on Sunday afternoon at the Jacksonville Landing complex in Jacksonville, Florida.

According to friends in the gaming community, the two men Katz killed in the tournament were Taylor 'SpotMePlzzz' Robertson, 27, of Ballard, West Virginia and Eli 'Trueboy' Clayton, 22, of Woodland Hills, California.

Katz - also known as 'Bread' - was in Jacksonville for the Madden NFL 19 video game tournament that was being held in a gaming bar that shares space with a pizzeria.

In the aftermath of the deadly shooting, chilling footage emerged showing Katz speaking after winning a chance to play in the Madden Club Series Championship in Burbank, California, in February last year.

Chilling footage has emerged showing David Katz bragging after winning a chance to play in the Madden Club Series Championship in Burbank, California, in February 2017

After defeating the number two seed 41-7 in the Bills Madden Club Round in Buffalo, New York, he told a reporter: 'I don't think of myself as a 7th seed.

'I think personally, I'm one of the better players – and I like to let my game prove that. I understand the game really well. My opponent probably should've called his timeouts… I took advantage that he didn't.'

Katz won $10,000 at the Buffalo Bills Madden Club tournament but lost in the quarter-finals in California, the New York Post reports.

When asked if he was nervous during the game in Buffalo, he said: 'Honestly, I felt like I had the ball most of the game. I wasn't really doing too much on defense.'

Shane Kivlen, one of Katz's gaming rivals and also the best friend of a gamer killed on Sunday, recalled the shooter as 'being kind of different' and said 'something was off about him'.

Kivlen told the Associated Press that Katz didn't talk much with fellow gamers, either online or when they met face-to-face for Madden tournaments, and much of what they learned about him was from his baffling style of playing the game.

He said Katz wasn't known to trash talk with rivals but after winning a championship last year he 'got up and let out the weirdest scream ever'.

An announcer for one of the gaming tournaments Katz previously played in described him as being 'not here to make friends'.

'He's all business, he's focused, and to even get him to open up to talk to you about anything - it's like pulling teeth, man,' the announcer said.

Katz had just been defeated by two players during the two-day tournament in Jacksonville on Sunday before the shooting spree unfolded.

About 150 gamers were competing for a $5,000 prize. The winner of the tournament would go on to a finals competition in Las Vegas with a $125,000 prize.

Katz won $10,000 at last year's Buffalo Bills Madden Club tournament (above) but lost in the quarter-finals in California. When asked if he was nervous during the game in Buffalo, he said: 'Honestly, I felt like I had the ball most of the game'

Katz (right) is seen in February 2017 at the Madden 17 Bills Championship, which he won. Police said he is from Baltimore and was in Jacksonville on Sunday for Madden 19

One gamer, who claimed to have defeated Katz the day before the shooting, told ActionNewsJax that he was acting 'weird' on Sunday and wearing the same clothes he wore the day before.

The gamer said that when he beat Katz on Saturday in the group round, he tried to shake his hand, but that Katz just stared back at him blankly.

Jacksonville Madden NFL shooting timeline Saturday, August 25: David Katz, from Baltimore, arrives at the Madden 19 regional tournament in Jacksonville. Sunday, August 26: Katz returns for the second day of the tournament wearing the same clothes as Saturday, and acting 'weird', a witness says. He is eliminated and returns with a gun. 1.34pm, August 26: The first 911 calls come in reporting gunshots in Jacksonville Landing. 1.36pm: The first officers arrive on the scene. They find three dead, including Katz, who is identified as the shooter. 4.30pm: SWAT teams finish clearing the shopping center. 7.30pm: Federal agents stage to raid Katz's family home in Baltimore. Advertisement

'He had shades on, he didn't speak to anybody. Even after we played… I went to shake his hand and just tell him good game and he just looked at me. He didn't say anything,' he said.

Another witness said Katz snapped after losing in the elimination round. The witness said he left the venue briefly, presumably to retrieve the gun from his car, and came back and started 'blasting everybody' in 'rampage mode'.

Like in Buffalo, viewers in Jacksonville could watch the games unfold online and see the players.

A livestream of the Jacksonville tournament caught the chilling moment a red laser dot landed on one of the victim's chests before the first of a dozen gunshots rang out.

Jacksonville Sheriff Mike Williams said investigators were looking into the video that appeared to capture the scene right before the shooting began.

Sheriff Williams said the shooter died from a self-inflicted gunshot.

Police have not yet confirmed the identities of the deceased victims but online tributes named them as Taylor Robertson and Eli Clayton.

Robertson was married and father to a young son, and had won 13 out of his 18 prior matches in Madden NFL tournaments, according to EA Sports. Clayton was a rising star in the Madden community.

A livestream of the Jacksonville tournament caught the chilling moment a red laser dot landed on one of the victim's chests before the first of a dozen gunshots rang out

Members of the Madden community say that Eli Clayton (left) and Taylor Robertson (right with wife and son) were the two people killed in Katz's suicidal shooting rampage

Eleven other people were wounded - nine from gunshot wounds and at least two others from fleeing the scene.

Marquis Williams, 28, and his girlfriend, Taylor Poindexter, 26, both from Chicago, were ordering pizza at the bar when they heard the gunfire.

Williams, who had participated in the tournament earlier, said people trampled each other in the panic while trying to get away.

'Initially we thought it was a balloon popping, but there weren't any balloons in the room. Then we heard repeat shots and we took off running,' Williams said.

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

'The tourney just got shot up. I'm leaving and never coming back,' Gjoka tweeted.

'I am literally so lucky. The bullet hit my thumb. Worst day of my life.'

Florida Governor Rick Scott visited several of the injured on Sunday night, including Timothy 'OLarry2k' Anselimo, who was expected to recover after being shot in the chest and hand.

The shooting took place inside a gaming bar inside the Chicago Pizza restaurant (pictured above) on Sunday afternoon

Katz carried out the attack on Sunday using at least one handgun at Florida's Jacksonville Landing, a collection of restaurants and shops along the St Johns River

Florida Governor Rick Scott (center) is seen visiting one of the wounded victims, Timothy Anselimo aka OLarry2k, in the hospital on Sunday as he recovers from being shot

Anselimo's mother posted this photo from the hospital showing his bloodied backpack

The sheriff's office used Twitter and Facebook immediately after the shooting to warn people to stay far away and to ask anyone who was hiding to call 911.

Police also barricaded a three-block radius around the shopping center. Officers and Coast Guard boats patrolled the nearby river.

Many ambulances could be seen in the area, but the shopping center area appeared empty of all but law enforcement. Police also took up positions on a bridge overlooking the river.

Heavily armed agents entered Katz's family home in Baltimore late on Sunday.

The agents wore bulletproof vests and brandished long guns as they entered the upscale town home complex near Baltimore's Inner Harbour.

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

Ivanka Trump sent her condolences to the victims of the shooting, tweeting: 'As we await further details, our hearts are with Jacksonville and all those affected by today's tragic mass shooting.'

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.

THE VICTIMS OF JACKSONVILLE MADDEN 19 SHOOTING Eli 'True' Clayton, 22 Clayton was a former high school football player who had won $50,000 playing Madden. He came from Woodland Hills, California, and had traveled to Florida to participate. Moments before he was shot, he was seen on a live stream of the tournament. The laser target light from Katz's gun was visible on his red sweatshirt. The young man was honored by the gamers he played with as a generous person who was friendly to everyone he met. One person described how he donated $100 to a GoFundMe page that had been set up for a family whose home was ravaged by a fire even though he hadn't ever met them. Another said he was 'always willing to help if you asked.' In April, after losing out on the top spot in a previous competition, he was gracious on social media and congratulated the player who did win. 'Not happy with the finish but I am happy with my growth as a person and the people I've met along the way,' he said. He had been playing Madden professionally for several years. Taylor 'Spotme' Robertson, 27 Robertson was married and had a young child. He lived in West Virginia and had traveled to Florida with the other gamers to take part in the tournament. He won the Madden Classic in 2017 and had amassed earnings of more than $80,000 since he started playing professionally. Other gamers said he participated in the tournaments to earn money to support his young family. It remains unclear what else he did for work. Robertson was sponsored by Dot City Gaming which confirmed he was among the victims on Sunday. 'They were great competitors and well-loved members of the Madden community. 'Our thoughts and deepest sympathies go out to their families, loved ones, and all of those affected by this tragedy,' the company said of both Robertson and Clayton on Sunday. Advertisement

Heavily armed agents entered Katz's family home in Baltimore late on Sunday. Agents wore bulletproof vests and brandished long guns as they entered the upscale town home complex