research - How to write a character that knows a lot about explosives?

I'm writing a story where the main character makes and detonates bombs. The character could be considered a terrorist. I want to portray the character as an expert, but I don't know a way to obtain more information in the art of explosives without it ending up with the FBI or something monitoring my searching.

Pairing terrorist, bomb, and how to, or instructions in the search bar seems to be a bad idea.

Any help on where to get info would be appreciated.