The officer pushes the man down, straddles the man and then punches him six times as other officers walk over to pull the officer off of the man.
A lawyer for Botham Jean's family claimed Dallas police conducted "common assassination-attempt" behavior following his death.
Take Back Oak Lawn group issues crime advisory alert after several attacks in recent days.
Five officers were killed by sniper fire during a peaceful protest in downtown Dallas.
Assailant was believed to have acted alone, and had no known connection to any terrorist groups.