Something like this happened in my town a few weeks after 9/11.
There was a loud explosion in a park area near a residential neighborhood and a man was seen driving off in a pick up truck.
Big media coverage and the guy turned himself into police. Turned out to be a landscaper who had legally obtained some explosives for removing stumps and he was wanting to see what kind of bang it made before he used them on a job.
We have/had/? one up my way (chester country, PA) who was setting off pipe bombs in several different locations .. one was found in a shopping parking lot
I don't think they every found him .. but someone was able to give a description of what he looked like