Weapons in the crowd?

So after blasting the crowd, the Marines didn't look over the edge of the wall and see even one weapon on the ground or in the hand of a dead body? In SJ's (Lt. Terry Childers') flashback he clearly see a lot of weapons in the crowd, and I am expected to believe that as the people in the crowd are getting shot, they all hid their weapons before falling to the ground and dying?

Oh and before dying, all the people with guns in the crowd had perfect aim, and none of them shot holes in the embassy wall to create bullet holes in an upward trajectory (this includes the one legged girl)!!

Makes absolutely no sense.