Revealing mistake: During the bunker siege, footage recycled from an earlier episode creates the sudden appearance of a white station wagon parked beside the police cruisers that isn't there in all the other shots. (00:41:40)
Continuity mistake: After murdering the cop, Frank and Luther steal a rifle from the squad car, then close the door. No one goes near the car again, but a few minutes later, the door has re-opened itself. (00:06:00 - 00:11:15)
Answer: He was fired. He never really appreciated his character. He felt Kono was portrayed as a big dumb Hawaiian and that the stereotype was racist. He also felt underutilized. He was fired after a heated argument with the show's publicist regarding his character. It seems there's not much details given regarding the incident or the firing, so it's seems possible he upset the show's producers as well.
Bishop73
No he said something derogatory about one of the Jewish producers that's why he was fired.