JACKSONVILLE, Fla. – News4Jax is learning more about the gunman suspected of carrying out Sunday's mass shooting targeting a Madden NFL 19 tournament at the Jacksonville Landing.

Jacksonville Sheriff Mike Williams said the shooter is David Katz, 24, of Baltimore, who appears to have acted alone in the rampage that killed two people and wounded several others.

Here's how commentators commentators at a previous gaming tournament described Katz:

"Man, David Katz keeps to himself. He's a man of business. Here's not here for the experience. ... He's not here to make friends. He's all business, he's focused. To even get him to open up to you to talk about anything is like pulling teeth."

Katz, who was found dead at the scene Sunday, took his own life with a self-inflicted gunshot wound inside the downtown Jacksonville venue, Williams said.

Williams said Katz used at least one gun, which multiple law enforcement sources said was a semiautomatic handgun, in Sunday's shooting. 

Federal agents raided Katz's home, which is located in Baltimore's affluent Federal Hill neighborhood, Sunday evening and were said to be interviewing the suspect's family.

WATCH: Report outside Katz's Baltimore home

Katz, a competitive gamer who goes by the nickname Bread, won the Madden NFL 17 Bills Championship tournament. He was registered to play in this weekend's Jacksonville event.

According to Baltimore Sun crime reporter Justin Fenton, court records linked to Katz's parents' divorce indicated he had "significant medical problems and healthcare needs."