The horror shooting took place at a gaming venue called Good Luck Have Fun inside Chicago Pizza in Jacksonville Landing during a live Twitch streaming of the event.

The LA Times reports that a gunman was a disgruntled player who had lost in the $5,000 tournament. They opened fire on others before turning the gun on themselves. Police fear there could be a second shooter.

In footage streamed online through Twitch nine gunshots can be heard before there are several screams and shouts.

As the shots sound, you can hear repeatedly “oh my god.” 15 people were reportedly shot.

Four people are feared dead with police confirming one suspect was pronounced dead at the scene, and they have launched a manhunt over fears a second suspect could be on the run.

Witness Ryen Aleman told CNN: “As I was going in the restroom, I stayed in there, and I just heard — there was just so many gunshots, at least 20 of them at the most.”

He said the shooter may have had a laser to assist his aim on the gun.

“I’m still shocked, I can hardly talk,” Aleman said.

The Jacksonville Landing is an open-air marketplace with stores, bars and restaurants in downtown Jacksonville along the St Johns River.

Police confirmed there had been a “mass shooting” at the centre and warned people to stay away from the area – but they are yet to confirm any details about victims. President Trump has been briefed.

Terrified bystanders fled the scene with officers finding them hidden in locked areas of the commercial complex.

SWAT teams are continuing to scour the area.

One witness said he ran so fast after hearing gunshot he lost his shoes.

The man, who didn’t want to be identified, said: “I was just getting my pizza and then heard shots. It was scary.”

Footage shows two young men playing in the Madden Championship Series when suddenly shots can be heard in the background.

The stream cuts out, but the audio is still live and people can be heard screaming out in pain in the background.

One person has claimed they were shot in the thumb and others have named a professional gamer who goes by the name ‘Larry Legend’.

His mother Sujeil Lopez was at her home in Tampa Bay when she got a call her son, who goes by Larry, 25, had been shot.

“I have to get to him. I am four hours away from him and I have to get to my son,” she told the New York Times.

“He was shot three times, once on the nipple, once on his hand and somewhere else.”

Memorial Hospital in Jacksonville, Florida is treating at least three patients that were involved in the gaming shooting, according to CNN.

Kyrie Curry shared footage the Twitch stream on Twitter, writing: “Oh my god someone just shot up the Jacksonville madden tournament. This is unreal I hope everyone is okay.”

Jacksonville Police wrote on Twitter: “Mass shooting at the Jacksonville Landing. Stay far away from the area. The area is not safe at this time. STAY AWAY.”

We can’t stress enough to stay away. Many blocks away,” they said in a subsequent tweet.

The office added in another tweet: “We are finding many people hiding in locked areas at The Landing. We ask you to stay calm, stay where you are hiding. SWAT is doing a methodical search inside The Landing. We will get to you. Please don’t come running out.”

CompLexity Gaming, which sponsored one of the players, confirmed the shooting at the event and said a gamer was “grazed in the hand” by a bullet.

Local news footage showed several ambulances, as well as firefighters and police officers, on the scene, as well as roads being blocked off in the downtown area.

The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) is responding to the scene in Jacksonville Landing, a law enforcement source told CNN.

Coast Guard boats are patrolling the river.