A dangerous person

Have you ever met a dangerous person and not known it at the time?

He wasn't dangerous to me but as a student I had a neighbour who shot cats, killed a goat in his backyard, drowned mice. He rented a room to a guy from church I thought I could be friends with, but he was a creep and I was dumb so I went to that old guy to get rid of him and stayed until 4 at night cause I was too shy to say hey gotta go to gramps, but lol sweet old grandpa told me the most gruesome stories and bragged and showed me how he drowned mice and that he shot the neighbour cats who were after his pigeons. I had a cat. Later I heard that he had been in prison for killing a guy and LOL he had said to that guy: She likes me more than you. Once he dropped by to ask if I could sew his pants, but I can't sew, so a roommate did it for sweet old grandpa.

Yes, there was a student in one of my classes who turned out to be a bad seed and looking back, I'm glad I was kind to him.

A former classmate of mine was once reported in paper as dangerous escaped convict.