I doubt he would have killed himself, had he not run into someone with a gun, that was determined to prevent him from killing any more. They commit suicide, once they know the rampage is all over.
Same happend to one of the two perps in the North Hollywood shootout. Heavily armed and armored, once out of ammo (full-auto uses it up in a hurry) and hit several times by cops, he wandered away and offed himself.
There is no question that he would have killed until he ran out of ammo. You don't bring 900 rounds to a suicide.