The Jacksonville shooter who killed two people before turning his handgun on himself on Sunday struggled at college and had "significant" medical needs which resulted in him undergoing psychiatric treatment, it has been revealed.

David Katz, 24, died on Sunday after shooting dead two competitors at the Madden 19 qualifier in Florida.

A fuller picture of his life began to emerge on Monday as the FBI raided the home his father lived in Baltimore, Maryland, according to the Daily Mail.

Richard Katz is a NASA engineer. He divorced David's mother Elizabeth in 2007. The pair have one other son, Brandon, 28.

Staff from The University of Maryland revealed how David struggled to keep up after enrolling in classes in 2014, three years after graduating from Hammond High School.

Before he attended college, he went to Sheppard Pratt Health System in Towson for psychiatric treatment. His parents made reference to it in divorce papers where they described his two stints there and the fact that he had been prescribed anti-psychotic and antidepressant medications afterwards.

He studied environmental science and technology and kept to himself, barely speaking to the other students or staff, they said.

"I knew the other students very well, but he did not open up the same way as the others did.

"I pulled him aside and asked if there was anything I could do to help and he basically had no reaction to that," Natalie Gill, a former teachers' assistant, told The Sun Sentinel.

She said that he thanked her at the end of the semester.

I thought, 'maybe I did have a little relationship with him after all.'"

Katz enrolled in 2014 but there is no record of him at the school this year nor is there any record of him graduating.

As part of their proceedings, a judge also ordered both parents to maintain health coverage for the boys who had "significant medical problems and needs."

Katz's mother worked for the FDA at the time of the proceedings in 2014.

No one from his family has yet commented on the shooting.

Officers were seen swarming around the three-bed, US$700,000 condo in Baltimore's inner harbor on Sunday night within hours of the incident.

Agents at the home wore bullet-proof vests and carried rifles and shotguns as they went into the property.

Reporters who gathered outside did not see any authorities carrying any bags of evidence outside, Fox News said.

A neighbour, Jerry Knauer, described Katz's father as a "really good guy" adding in a video interview that "he's been really nice to us".

Another neighbor told DailyMail.com that Katz had been about 17 when the family moved into the neighbourhood about six years ago.

"Nothing suspicious, they just seemed like a kind of quiet, normal family," the neighbor said.

The shooting broke out as the tournament was being live-streamed around the world and a game was in progress.

In footage of the tournament, one of the players is seen with a dot that appears to be a laser pointer dancing on his chest and neck.

As the live video shot cuts to the action on the virtual football field, gunshots and chilling screams can be heard in the background.

The commentators can be heard going silent as the first gunshots are fired and people begin screaming.

The stream then cuts off and a message appears saying "controller disconnected".

One witness told CNN he saw the gunman shoot multiple people before killing himself and that it appeared he had a laser sight on the gun to help him target victims.

Police arrived on the scene within two minutes of receiving the first 911 calls at 1.34pm, Sheriff Williams said.

Witnesses said people trampled each other while fleeing the gunfire.

Marquis Williams, 20, says he and his girlfriend, Taylor Poindexter, both from Chicago, were ordering pizza close by when shots erupted. He said Sunday that he didn't think it was gunfire at first.

Says Williams: "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."

WHERE TO GET HELP:

If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.

OR IF YOU NEED TO TALK TO SOMEONE ELSE:

• LIFELINE: 0800 543 354 or 09 5222 999 within Auckland (available 24/7)
• SUICIDE CRISIS HELPLINE: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• YOUTHLINE: 0800 376 633 ,free text 234 or email [email protected] or online chat.
• NEED TO TALK? Free call or text 1737 (available 24/7)
• KIDSLINE: 0800 543 754 (available 24/7)
• WHATSUP: 0800 942 8787 (1pm to 11pm)
• DEPRESSION HELPLINE: 0800 111 757
• SAMARITANS – 0800 726 666.