They sucker-punched him. What classless a-holes.
While I’m no Cam fan, he didn’t deserve that, or at least not from what the video shows. Did he provoke them somehow? That’s a question for others to answer.
That’s Good Sports breaks it down.
If you’re writing about the guy in the white shirt that came up later, I actually thought that too but if you look closer, he’s actually hitting the other guy that Newton is tied up with; coming to his aid. 
You can tell this by what he did after the others got there too, because he wasn’t paying any attention to Newton and was trying to track one of the two that were getting after him.
Cam, being a classless jerk? Color me not surprised. Still, that doesn’t excuse the other coaches’ actions.
Remember the good old days when coaches used their teams to do their talking for them? Buddy Ryan vs. Jimmy Johnson? Now THAT is the way you go after other coaches!