"Shoot to kill", if required by the situation, has always been amongst the options open to the authorities. But if, as some here intend, it's to mean on-street executions then no, that's not right, it's not what we do and it's not even a militarily advantageous course of action.
Why not? Firstly it's exactly what our enemies want. They yearn for martyrdom and wish to be viewed as warriors rather than the low-life criminals they are. But mainly because that's not how we've chosen to run our society. We have decided that even the most wicked criminals are, if possible, committed to trial then locked up, until they're forgotten, shuffling and incontinent. If our view changes on that, let it be because of reasoned debate and consideration. Not because some bearded nut-job with an AK47 wants us to.