Would they charge someone with murder for this?

Just wondering. Lets say a guy tried to rape a girl but she got away. She reported this to the police. Then later the same dude saw her while she was waiting for her boyfriend outside a store and tried to rape her again. Her boyfriend came out and attacked the guy. The guy beat her boyfriend up. Then her boyfriend picked up a metal pipe and bludgeoned the dude to death. Would he get manslaughter? Or would it be self defense? What if he threw the body in the river? Just wondering because im watching this show and that happened. They are all scared they are gonna go to jail. But i woulda just called the cops since thats self defense right?