David Katz, the suspect in the Jacksonville mass shooting, was reportedly introduced at the video game tournament as a "man of business" who "keeps to himself".

The former eSports champion had travelled from Baltimore to Florida intent on taking part in the regional qualifier of the Madden 19 American football tournament, hoping to make it through to the finals in Las Vegas.

Instead the 24-year-old was eliminated, according to witnesses, who say he later returned with a handgun and opened fire. 

The outbreak of shooting was captured on a live stream of the event, with several gunshots heard in the disturbing footage before the feed was disconnected.

Just before the shots were heard, a red laser…