Caveman investigator : History 1st Murder

Someone got brained in the grotto your tribe of cavemen live in. It's up to you to conduct the first criminal investigation in human history, to figure out who is the murderer. Get your prehistoric brain to work to find out the criminal mind that commit such act. Be smart (as far as a caveman can be), and invent the tools (made of flint and stones) and method (ever done a police sketch on the walls of a cave ?) to catch the killer.