Why would a guy touch a girl from behind and run off pretending its not him before she could turn around?

He is my General Manager. I dislike him and avoid talking to him. He doesn’t act like a pervert though. But I know he is very “close” to another coworker. If she or any other employee is texting during work, he allows them. If he sees me texting or smiling at a text, he throws a non-verbal fit. For example, when he was angrily throwing things near by me and stomping off, or shouting at someone else about something dumb. But never says “get off the phone. ”
I suspect he have aleady slept with the other cowoker. She is very cherpy all a sudden, and they talk to each other in a low voice while standing close. When it comes to my interaction, its cold from my side. But I don’t want to deal with him. But I love my job and have been there longer than him. (I am hoping he transfers. Hence, the reason why I stay). He finds dumb ways to touch me or talk to me when I avoid him.