Perhaps you are familiar on what happened at Libery Chowk ........ let me give me some info and the you can perhaps comment once you have proper information.
The Sri Lankan team was in the "big" bus ....... while as Chris Broad along with the othe officals / umpires were in a "smaller" bus following the team "big" bus. The Sri Lankan team bus made it to Gadaffi Stadium ... while as the "smaller" bus driver was killed and so these guys were stuck in the middle of the gun fight. It was only when the gun battle stopped that these guys were rescused. hence the "sitting duck" comment...... hope this clears the situation ....
So, if the bus was a sitting duck, why did not our 12 bearded commandos attack and kill all inside? What prevented them from doing so, since they seemed to be in no hurry?
The priority of a security detail is to protect the VIP which includes evacuation. Their job is NOT to fight a war or kill and arrest the attackers, that would be stupid. US Secret Service guy as you know are trained to cover the president's body with their own, not pounce on the attacker.
The job to engage the attacker, falls on the counter assault team, which seems to have either not existed or completely failed in this case. Or maybe those were the 6 who were killed.