The IS claims are sketchy.
ISIS in recent months has made a number of demonstrably false claims for attacks and incidents that had no jihadi terror nexus.
Exhibit A of a false ISIS claim was their claim for attack on Manila, Philippines casino resort in June. ( was an indebt gambler)
Exhibit B of a false ISIS claim was their claim to have smuggled explosives into CDG airport in Paris last month. ( was a drunk woman being abusive after being denied a flight)
ISIS, desperate for attention, will claim just about anything these days knowing their supporters won't believe government/media.
I can't think of a single case in which a jihadi terrorist shot themselves dead after an attack. A big theological no no for jihadis.
Jihadis make distinction between suicide, which they believe forbidden by Islam, and death as byproduct of "martyrdom" bombing/attack.
Be keen to see what the police turn up when they start going through his phone/computers etc