If someone is suitably high, shooting _at_ them 45 times may very well be needed to stop their assault. Not every shot may connect, not every hit may be immediately decisive - especially if the body is confused enough to not be aware it should stop. If there isn’t a central nervous system hit, nor a mechanically disabling hit, then you’re just waiting for the perp to bleed out or quit.
According to the full article, seven New Jersey cops fired a total of 69 rounds, 45 of them hit the perp.
Watching the dash cam video, it appears that even after the perp fell, he was still trying to raise his weapon, so several more shots were fired at him while he laid on the ground.