While exploring last night I came upon that waste disposal site just South West of the Republic of Dave when this guy ran up to me, said he had explosives tied to him. I could not even click on him before he ran off and blew into a million pieces.

Would anyone happen to know anything about this?

It is a random encounter that can happen any where, at any time and more than once per playthrough.

Random Encounter.
If you have a high enough Science and/or Explosives skill, you can disarm the bomb. (Can't remember the exact requirements) If you disarm the bomb you get a variety of prizes: all random. I've received a Nuka Cola, a piece of food, coordinates to Oasis or a location marker for Mirelurk Treasure. Don't trust that last one, it's a mirelurk king war zone.