Knife/any murders. is it time for capital punishment for those found guilty

[mtread]

and charged the police car as it pulled up, knives in hand, with the intent to kill or maim them

No they wanted the police to open fire and die as martyrs. They were terrorists.
While we're talking about Lee Rigby, nobody seems to have mentioned the premeditated, cold blooded public murders of Jo Cox and Makram Ali. I wonder what caused those murders?