Denis Leary recently teased how the series finale of 'Rescue Me' would end on 'Late Night With Jimmy Fallon' but didn't reveal just how heartbreaking the show's final bow would be.

Spoilers ahead:

In this scene from the finale, Leary's character Tommy Gavin awakes at the bottom of a collapsed stairwell after a massive explosion while battling a fire. Franco, Sean, Mike and Black Shawn emerge bruised and battered, but alive as well.

However, Lou, Tommy's lieutenant and best friend, isn't as lucky, and died while trying to protect his firefighting brothers from the blast.

Tommy discovers Lou's badly burned body among the rubble. He even attempts to shield the survivors from the gruesome scene. (Warning: The clip is a bit NSFW for graphic sequences.)

[AOL Television]