Apparently the justification for shooting so often, & to the head, was to ensure that he could not trigger the(suspected)bomb.
But, if he HAD been a suicide-bomber, wouldn't shouting a warning ("armed police, don't move") have been likely to cause him to trigger the bomb?
In that scenario, you need to disable hime BEFORE he realises that he has been spotted.
The surest way to instantly disable him is to shoot him dead.

Of course, you might not want to admit that afterwards...