After lots of foreshadowing and plenty of fan speculation, NBC tearjerker "This Is Us" finally explained how Pearson family patriarch Jack (Milo Ventimiglia) died. And in keeping with the show's penchant for heartbreaking drama, the long-awaited revelation left viewers devastated.

The episode, fittingly titled "Super Bowl Sunday" (since it aired after NBC's broadcast of the Super Bowl, and also took place on the day in question, both in the '90s and in the present day), picked up right where last week's installment left off, with the fire started by that now-infamous Crock-Pot tearing its way through the Pearson house. Jack wakes suddenly from his slumber and stumbles to the door, opening it to discover flames roaring up the stairs and into the hallway, headed straight for Kate and Randall's rooms.

In true Jack Pearson fashion, the patriarch doesn't waste any time springing into action, instructing Rebecca (Mandy Moore) to wet some towels and immediately running to rescue Randall, then Kate. (Kevin is out for the night with Sophie.) By the time Jack reaches Kate's room the flames have spread even further, and the mattress he uses to shield them as they run catches fire, too, burning his hands and arms.

But finally, everyone is back in Jack and Rebecca's room, and Jack fashions a rope out of some bedsheets, lowering his family one by one to safety out the window. He's just about to jump down himself when Kate cries out for her beloved dog, Louie, last seen slumbering on the first floor. Seeing the pain in his daughter's eyes, Jack decides to run back inside, and search for the pup.

That seemed to confirm fan theories that that was indeed what killed Jack (and why Kate was so guilty), but if you think Mr. Pearson is done just yet, you're wrong. A couple excruciating minutes later, Jack heroically bursts out of the house, carrying Louie, as well as a pillowcase full of family mementos, including a photo album, Kate's audition tape, and Rebecca's moon necklace.

Unfortunately, though, that act of selflessness and bravery (and some would say foolishness -- seriously, why risk running back into the house, Jack?!) is ultimately what causes Jack his life. He inhaled quite a bit of smoke while hunting for the dog and keepsakes, and what starts as a routine check at the hospital for his burns and monitoring his lungs, turns into full-on cardiac arrest. All that smoke he inhaled put too much strain on his heart and lungs, and Jack Pearson died of a heart attack.

It's a moment, mercifully, that we don't have to see unfold onscreen, though we do witness Rebecca's breakdown when the doctor has to tell her the news. And the fans who could stop themselves from sobbing long enough to update their Twitter feeds could relate to her pain.

Thankfully, Milo Ventimiglia was there to assure fans that Jack wasn't leaving the show (there are still lots of flashbacks waiting for fans), and his spirit would certainly live on despite his death.

Fans won't have much time to recover: "This Is Us" is back again on Tuesday for another new episode, this one featuring Jack's funeral. Better stock up on tissues again now.