The trooper who PITTed her was shaken up when he got out of his car? He took his time walking around the car and drawing his sidearm, it seemed. Or did he just know they weren’t going anywhere fast?
I would expect he may have been a little dazed knowing he might have just taken three lives. That's something nobody wants to do, but he knew he was protecting other lives by doing it. Probably took a few seconds for that to all come together in his mind.