EDIT: New Theory Discovered.
Hi fellas, new to the forums but I decided to make a post speculating a few thing, Mostly to do with Johnny Klebitz.
For a start Johnny Mostly resembles John Marston, the Protagonist from Red Dead Redemption. It isn't a strong resemblance but here is a snippet I got from the Red Dead Wikia and GTA wikia.
Basically Johnny underwent what John did, they both lived rough lives and did rough things throughout the story line and in the end they both died defending what they loved. Except they both died differently, John by a U.S firing squad and Johnny by a facial stomp.
Also, for Johhny's death I think rockstar may of pre-planed it, a hint being one mission in TLAD where you save Ashley from some drug dealers, Ashley mentions that Johnny and her should ride off into the sunset before Johnny remarks that she'll still be hooked on meth.
So this speculates something that we should accept Johnny's death in some way (and I'm not Implying that we completely say "Omgz trevar is da best liek f*k jon boiii) but I guess he "died" for a cause.
As for dying, I'm not sure he's really dead.
Notice when he shot him the game actually registered it as a death, perhaps we can speculate something here?