If your objective is to make a statement or prove some kind of point, but you aren't really looking to hurt or kill anyone, I could see it making sense. Like if McVeigh (if you buy the official story) had warned everyone in the OKC Fed building to get out first, and then blew the building to strike a blow against the Fed infrastructure, but wasn't so far gone that he wanted to actually hurt people, just the institution. Not saying that's what happened in Nashville, just that I can see a possible scenario where someone might have wanted to make a political statement or cause some sort of property damage, but wasn't comfortable with the idea of hurting people. Having it give a warning first seems like something you might do if that's your line of thinking.

If your objective is to make a statement or prove some kind of point, but you aren't really looking to hurt or kill anyone, I could see it making sense. Like McVeigh (if you buy the official story) had warned everyone in the OKC Fed building to get out first, and then blew the building to strike a blow against the Fed infrastructure, but wasn't so far gone that he wanted to actually hurt people, just the institution. Not saying that's what happened in Nashville, just that I can see a possible scenario where someone might have wanted to make a political statement or cause some sort of property damage, but wasn't comfortable with the idea of hurting people. Having it give a warning first seems like something you might do if that's your line of thinking.