This video shows that one of Kenneth Gladney's attackers was a tall, stocky dark-haired man in a deep blue t-shirt (an SEIU shirt which read "HEALTHCARE '09") who pushed him down and either stomped him or tripped over him.
At the very start of the video, a man is on the ground in a blue shirt and tan pants. Another man steps across him in what looks to me like a protective maneuver since his attention is up and away from the prostrated man.
Notice that in the shadows on the right, Gladney is in a khaki t-shirt, squatting in a defensive position with his back to the camera. There seem to be some blows. Then the tall man in the deep blue t-shirt comes from the far right, from behind Gladney, yanks Gladney back and shoves him to the ground. The attacker then stumbles to the ground himself. All this happens in the first 10 seconds of video.
It's good to see these townmeeting participants are actively being good citizens, by protecting those two or three men who are being attacked. One woman who shows good sense is wearing glasses and an open white blouse. She seems to get between the man in the deep blue t-shirt, after his stumble, and Gladney.