It might have been useful to question this (supposed lone-wolf) apparent 'terrorist'. It might not have been that useful. Or it might just have been possible to glean something that saves other lives in other potential incidents further down the line.
TBH, I'm not convinced on this occasion - but we will never know now.

Some Police need to be armed, in some locations / situations.

More generally, perhaps some investment / research / training in way more efficient instant stun weapons might be better than creating a mini USA (no thanks).