Here's a breakdown on the case from USA Today.
https://www.msn.com/en-us/news/us/prose ... li=BBFoJB6Arbery apparently suffered from an undisclosed mental illness. And had been arrested previously from carrying a .380 semi-automatic pistol to a basketball game at a highschool he did not attend at the age of 19. While the article names him as Ahmaud M. Avery, this was acknowledged as an error by the paper and corrected to Arbery at a later date. In any event by looking at his mugshot, you can tell it's the same guy.
https://www.news4jax.com/news/2013/12/0 ... ball-game/Another article I ran across mentioned that his shoplifting arrest also coincided with a probation violation. It's unclear if this is a separate charge or related to the gun possession.
So basically, you had a mentally ill guy with a criminal record wandering around a neighborhood he didn't live in. He was probably acting strangely (i.e. looking inside a construction site while out jogging) and it set off the locals who said they had experienced a series of local burglaries.
The locals go out to hold him until the police arrives.
Arbery gets agitated and apparently tries to grab the shotgun one of the men is holding. In the process of the struggle, he is shot.
It's an unfortunate example of what happens when the mentally ill don't receive proper treatment.