A husband discovered his wife in bed with a neighbor. the neighbor ran out the back door. the husband screamed at his wife and vowed revenge. after consuming several drinks to build up his nerve and becoming intoxicated, the husband went to his friend's house and borrowed a gun, and then went to the neighbor's house. the neighbor had neglected to lock his front door, so the husband walked in. he found the neighbor trembling in the living room and pointed the gun at him. the neighbor immediately began apologizing and pleading for his life, but then suddenly he pulled a switchblade knife from his pocket. as the metal flashed, the husband fired a single shot at the neighbor, killing him. what is the most serious crime of which the husband can be convicted?