I saw this on TV when I was pretty young, I would guess 1974-1976. I’m pretty sure it was a movie or a TV movie, or maybe an anthology episode, but not a series episode. It was in color. There was a guy who was a killer bomber and/or arsonist in some city, he left bombs in brown paper packages and blew people up. I think he was kind of nerdy, with glasses. I don’t know if the movie was all from his point of view or if it also followed the cops trying to catch him, but it followed the killer quite a bit and he made the bombs. He met a young (neighbor?) kid and kind of made friends with him, but the kid ended up getting burned up by one of the bombs, maybe by accident. I recall the killer also set up a bomb that was triggered by a car tire backing over it, and also there was some scene where there was some kind of device where someone dripped some chemicals on it from an eye-dropper and it either started to burn or made poison gas.

I know this is obscure, but thanks for reading!