A Signal safety number is a unique number that verifies the security of messages and calls between two Signal users.
Matthew Livelsberger Aka Matt Berg changed his Signal safety number just before the explosion And then his photo and safety number changed AFTER the explosion.
Clearly this was manipulated by somebody other than him, as he was deceased and would not have been able to change anything. Find who changed his signal info and you find who shot him in the head.
He was Special Forces long enough to understand basic explosives. He was trained in Home Made Explosives (HMEs). He could have gotten everything he needed from a local hardware store to level the entire bottom floor of the Trump hotel. There is simply no way he thought the combustibles he had in the back of that Tesla truck would have been enough to do any damage to anything.
Other Green Berets that knew him are convinced that he could not have done this, nor would have had any reason to do so. He just had a 6 month old baby with his new wife, and had a literal multitude of jobs ahead of him when he retired.