There was no penality on the play (there was a ref at the bottom of a pile). Dunn was trying to get up from being in the pile and I think the player that was holding on to him wasn't letting him get up so he kicked him.
It is also entirely possible someone was trying to bite him, yank his foot as to injure him, or scratching him. I wouldn't put anything past Tampa. It is also possible that Dunn was just retaliating against a Tampa player for poking Rossum in the eye.
That's what I saw too...