After the gunmen burst in to the gallery, Steve tells Kono to nod if all the hostages are ok, which she does. However earlier we saw two people being hit in the chest by the gunmen's automatic gun fire.
When Jerry's van hits the aid vehicle being driven by the art thief, the scene from behind and from the side show the aid vehicle hitting both parked vehicles. The next scene is from the front, showing Jerry's van ramming into the vehicle and then into only the car in the second position. The car in the front position is not hit in that scene angle.
When giving a rundown of the suspects and their positions McGarrett says "We've got six threats all armed with Steyr machine pistols...". Janssen is armed with a 9mm pistol and at least two other of the robbers are armed with Mini-Uzi submachine guns. An experienced SEAL/cop like McGarrett would have known the difference.