I would favor restraining yourself in that situation. What if the thug has a friend, and you're out of ammo? Trayvon became a much better member of society after one shot, so why give an overzealous prosecutor any reason to question your actions, and why waste ammo when it is in short supply?
I strongly approve of good shot placement, so that your shots will permanently stop the threat, but you have a legal obligation to stop shooting once you have stopped that threat. You should reasonably be able to fire a second shot and argue that the thug was still acting in a manner that posed a threat when you pulled the trigger, but more than one shot after a fatal round that completely disables a criminal may be pushing your luck.
Serino had interviewed John Good and others before he interviewed GZ.