There is a public safety exception to this rule, in that if it can be reasonably demonstrated that there was some imminent danger to the public, a suspect may be questioned about things like "where is the bomb?". If he says "it's under the boat", that statement can be used against him even if he didn't invoke on Miranda warning.
So there's really no point to read him Miranda this early in the game, unless someone doesn't want him to talk and hopes he lawyers up.
The remedy for a Miranda violation is to not admit the statement or anything derived from it into evidence (fruit of the poison tree). If they’ve got the guy on video dropping the bomb plus other evidence, they don’t need his custodial statement to convict him.
Now, what might be going on is that he clammed up and they’ve Mirandized him so they can appoint a Public Defender who will tell him either (1) STFU until there is an agreement to not see the death penalty or (2) spill his guts so he has a chance at avoiding the death penalty.
Give him a quick military trial and shoot him at dawn. Who does the creep think he is, O.J. Simpson. Why should he have a trial that drags on for years.