‘I’m going to kill you all’ isnt specific.

If you claimed a means, like shooting, or blowing up their meeting place, espespecially if that means is available to you, that adds credibility. P

Immediacy / timing is usually needed as well. ‘One of these days im going to chuck a grenade through the window’ Vs

“If yall protest the civil rights march in Memphis, im going to use you for target practice”

Is probably going to get a knock on your door.