Trooper Sergeant was an NPC, the leader of the squadron of Clone Troopers who investigated the holding cells when Greedo/Fake!Han Solo, Adam Lars/Luke Amidala/Luke Starkiller, and Chewbacca broke into them.
A New Generation Edit
When the Clone Troopers arrived at the holding cells, they found the entrance sealed. The Trooper Sergeant ordered the sealed door blasted open. It was, but Han shot the first two Clone Troopers who tried to enter. The Trooper Sergeant fired in the air and declared that this was his last warning shot and that if Han and the others kept killing his men, he'd have to be aiming at them.
It's unknown if the Trooper Sergeant survived the laser fight with Luke, Han, and Chewbacca. If he did, then he would later have been killed along with everyone else onboard the Peace Moon when Luke blew it up. Either way, he's dead, Jim.