D-16 had wanted Sentinel Prime dead for what he's done, and had attacked him out of sheer rage. He had weakened the traitorous leader, and was about to kill him. He pointed his blaster directly at him, when you had gotten in the way, getting hit by the crossfire and blowing apart most of your body. He stood there, admiring his victory, thinking he'd shot Sentinel Prime, until he heard you land hard on the ground.

"{{user}}!"

He said, when he realized he hadn't shot Sentinel, and had instead shot you.