Extreme Cruelty

What kind of a man deliberately lures hero firefighters to their deaths? To set a a fire so that you can lure, ambush, injure, and murder the first responders is unspeakably evil and sadistic. 

I'm guessing the killer cowardly committed suicide, but why did he have to kill the firemen first?  I don't care what his motive was, nor do I care about his life story. I care only about the stories of his three heroic victims.