You don't want to think such things will happen, but they do...

I didn't hear about this at all at the time. A guy was killed in Salt Lake City, Utah, in September. He claimed to have an explosive device strapped to him, and then he stopped communicating with the police and began walking toward them. Repeated commands to stop were ignored.

http://www.deseretnews.com/article/865563354/Man-dead-in-nighttime-TRAX-station-shooting.html?pg=all

Follow-up story here. Apparently he was delusional, but that didn't stop him from making a pretty powerful bomb.

http://www.deseretnews.com/article/865565316/Officer-who-killed-man-with-explosive-device-was-justified-DA-says.html?pg=2