If he possessed the bombs claimed, or control devices for IED remote detonation, the shaped charge weapon used would increase odds of removing that particular threat. Allegedly materials were found at his residence backing his claims of producing explosive devices.
That’s another reason I question the “pound of C-4” fact. If he had explosives on him, a blast of 450g of C-4 could have triggered a much bigger explosion.
A small shaped charge would have reduced that chance.