A gun shot to the chest is somewhat bizarre, especially for a male. Men tend to shoot themselves in the head to make sure the job gets done with one shot. It would make me a little suspicious of it being a suicide.
Dave Duerson, who played for the Bears in the Jim McMahon era, committed suicide a year ago in this manner specifically so his brain could be studied for signs of brain damage due to some sort of chronic traumatic injury syndrome
https://www.suntimes.com/sports/5141748-419/study-dave-duerson-had-brain-damage-at-time-of-suicide.html
very sad