Killer was created in Episode 6, on Isla Muerta. After learning that Velociraptors needed more than one, Dan also created Jan.
In Episode 7 Killer escaped and killed three people before being tranquilised and put back in his enclosure.
In Episode 9 he escaped again with Jan, but didn't kill anyone due to be tranquilised by Dan before leaving the enclosure. To keep the raptors busy, Dan introduced two Ceratosauruses into their enclosure, called Killer Killer and Jimmmm. Killer and Jan now spent most of their time fighting the Ceratosauruses off while living in a state of perpetual fear.
Killer was senn again in Episode 26, when Dan returned to Isla Muerta. Dan introduced three more raptors to the enclosure, but all three were killed by Killer Killer and Jimmmm. At the end of the episode Jan was also killed.
In episode 27, Killer was finally killed by Killer Killer.