Putting supposition to one side what we do know is that Mr Cooke and the other two guys who found themselves in the same position (one of whom is a 72 year old pensioner) were arrested, locked in a cell for 24/48 hours and then released on bail - this did not need to happen.
One wonders what kind of evidence the GMP have that Mr Cooke may have committed murder (it is suspicion of that crime he was arrested for). Going back to supposition - maybe while Mr Cooke was in his lounge on Saturday afternoon watching the box, he phoned his neighbour and said "by the way don't come knocking on my door this afternoon because I'm going to stab the next person that does to death"
Mr Cooke and the other brave guys should be treated as victims of crime not criminals.