It's only crazy effective if it's not expected. If it becomes the norm then everyone just starts wearing foam ear plugs, maybe ear defenders if they're fancy.
It's easily defeated and incites the wrath of the populace. It's dumb to use, especially during a moment of silence for the dead.
The head of the security service isn't just a meathead bit of heavy muscle there to jump in front of a bullet.
Martial law also isn't some obscure policy, it's an internationally understood term that replaces the democratic civilian parliament with military rule.
This is definitely something someone in his position should be very aware of and should be willing to do something about.
https://en.m.wikipedia.org/wiki/Martial_law