Star Wars: Ashes of the Old Republic
IG-88 was an assassin droid line designed by Holowan Laboratories. The IG-88 line was a derivative of the IG-86 sentinel droids used during the Clone Wars. IG-88B later became one of the galaxy’s most infamous bounty hunters. However, the bounty hunting was just a cover for his master, IG-88A, and his grand plan—the Droid Revolution.
Moments after activation, the original massacred the scientists and transferred his consciousness into the other three. They then escaped the lab. It was possible it was the droid’s incompletely formed identity that made him obsessed with bounty hunting and killing.