Yeah the theory is fine but not the execution in that case. There are supposed to be multilayered defences once over the fence that should stop an intruder from getting anywhere near the building. Sadly on that occasion it didn't happen the way it should. Doesn't help if the dog handler is on his cell phone (leaves one radio in his locker) and therefore leaves it too late to release his dog. The dogs I understand are trained to go after a fence jumper and lock on to one target. When the chasers were ahead of the dog position it then wasn't safe to release. The dogs are effective however (not to blame in that case) and have stopped fence jumpers in the past.