TN+Homicide+Scenario

John Crocket, a perfect citizen with no outstanding offenses, comes home from his construction site and goes into his house...his wife is in the other room with another man. John goes to his gun rack and pulls out a gun. He goes into the other room and viciously murders the two people in the room. He was perfectly sane and even told the officers he was glad of what he did and was completely aware of the possible consequences the whole time. If this was a case in PA how would he be punished?