I dont know if its the order I did things that led to this,or the reloading,or whatever,so Im just going to tell how it happened:
After killing lilith,looting her safe,and taking money from the shady guy,I exited blackwater through the north(a small pass in the mountains),and the shady guy appeared with his thugs.After killing them,I had a few more things done,and a few reloads(I even ended the game and restarted it later).After a bit,I was again in blackwater,and exited through the east(following the path),and the shady guy appeared AGAIN.Same guy,same dialog,same thigs.Now I have his blood on both paths
My guess is that the trigger up north didnt cancel the event to the east,but wheter this was because of reloads or not,I have no clue.
Also,could this one be made to trigger even if you use quick travel?Because now it can be avoided like this forever.