And the legal investigation can find as such. That's what legal processes are for.

The fact that the police are protesting the legal process, as opposed to a conviction is terrible.

Also, the fact that the guy was a criminal does not make it ok for the police to use their weapons and kill him. In fact, if he was indeed fleeing then that almost certainly is against the rules they are required to follow in the UK as part of the wide latitude to inflict violent force that is granted to the police.