Officers like trained civilians are trained to stop the threat. A close incoming individual with a knife, club ,etc is stopped when they go down , or turn and run. What usually happens , is multiple officers , using high cap handguns, all firing at once until the threat goes down or turns and runs as trained , equals more rounds fired than actually needed. Alot of subjects are shot several times as they are falling just due to the rate of fire from multiple weapons. That's not the same as firing 30 or 40 rds blindly as also happens.