I'll try and spell it out for you.

Toolson = the digger/shooter
SVU = the buried corpse
Taking one last 3 = shooting the corpse in the head

There was literally nothing SVU could do about their situation, just as there is literally nothing a corpse can do about his -- both have already been "killed."

"But the SVU guy was still playing D! He was trying to get a steal!"

So? What exactly can he acheive? He can get a steal and maybe one more basket before the buzzer. That changes aboslutely nothing about the game or SVU's situation. They were still done, dead, muerto. Toolson shooting a 3 at the buzzer when the team was up by 50 points (and thus had already "killed" SVU) is equivalent to shooting something that is already dead. Trying to steal the ball and take one last shot doesn't change the fact that SVU was already dead.