The Bomber and Mrs. Moroney - S3-E22
Continuity mistake: The bomber wants revenge on Danno for killing his brother, Joey Collins, whose death is recapped in flashbacks to a first season episode in which Danno first killed someone in the line of duty. But in that episode, Joey's name wasn't Joey or Collins - it was Thad Vaughn. (00:22:00)
The Bomber and Mrs. Moroney - S3-E22
Continuity mistake: The HPD snipers watch McGarrett's office window, trying to get a clear shot at Collins. In camera views from inside the office, there's a coat rack with a hanger on it standing in front of the window. But in all the shots from the snipers' POV, the coat rack isn't there. (00:40:00)
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.