Two different situations.
These nikkas ran up on 2 stains (in his draws) like some fukkin vietcong.. like literally running AT him with the burner from out of nowhere, he ran off instinct, this was some animal planet, cheetah/gazzel type action.
That's different than some nikka that was already standing next to you like some extra in a movie and all of a sudden turning the situation into a robbery. And unless i'm completely off on the accounts it wasn't nowhere for pac to really run to. Being that he was trapped and nikkas ain't have to rush the operation he had more reaction to think about the fact that he had guns, and that these nikkas might kill him anyway. He even had time enough to peep that fact that everybody else with him were acting guilty and bytch made and were probably in on the set up.