What should i name my characters?

i want to write a book about a group of kids who get murdered and the killer blames it on the kid's friend Lizzy. There are two cops. One bad, one good. One who believes that Lizzy didn't do it, and one who has spent every fiber of his being trying to get a confession out of her. They are both male and i was hoping for short names (four letters tops). I have been thinking for three months and nothing seems to fit. Any ideas?