This happened to me, too. I was leaving my team near my car at the gas station before venturing to Navarro. Vic started shooting at me and my other team members, also left to stand there, killed him.
I'm playing Restoration Project 1.1 now, so I figured it maybe has something to do with this. Guess not.
This is probably due to performing some acts Vic doesn't particularly approve of. Somehow the game often only processes that after you kick them out of the party.