Please check this

Red, now armed with a knife, runs down the hall, turns a corner, and collides with one of the bank robbers. Red swings the knife at him. The bank robber stumbles back, firing into the ceiling. He jumps back to his feet and fumbles with his rifle. Before he can get it under control, Red charges at him and stabs him in the chest. Just then another bank robber appears at the end of the hall, firing at Red, who takes cover behind a vending machine.

1) Is "stumbles back" okay to mean that he falls on his ass?

2) Is there anything that doesn't work and that you think I should change?