That's the questions viewers of "This Is Us" have been asking since learning Milo Ventimiglia's character died before any of the present day scenes.
So far, fans don't know much, but that hasn't stopped them from trying to figure it all out before the show's big reveal.
TooFab has scoured Reddit for some of best fan theories so far. From the shockingly possibly to the most unlikely, see the 6 most interesting possibilities below.
Jack Committed Suicide
This is definitely the most grim path the show could take, but creator Dan Fogleman did promise some "dark" moments ahead. And if you look back at the episodes we've seen so far, there have been a few clues from his kids that could hint at Jack taking his own life.
First, Randall talked a man off the ledge at his office Christmas party, telling the guy his daughter would be able to forgive him for an affair or money issues, but not suicide. Could he be speaking from experience?
Randall also wanted his birth father, William, to have a nurse so he didn't "die when nobody's lookin'." Dying alone doesn't automatically mean suicide, but fans have still cited it as possible evidence.
As for Kate, Toby's admission that he considered suicide weighed heavily on her, prompting an unexpected conversation about the specifics of his depression.
And Kevin seemed to express some anger over his father's death, telling Olivia that he threw away all the model planes they made together.
While some of the evidence adds up, there's just one thing that doesn't: it'd be so out of character for Jack. This man lives for his wife and children and it doesn't seem like there's anything they could do to change that.
This theory gained popularity after Kate had a freakout on an airplane in the first half of the season. This could also explain why Kevin threw away all the model planes.
Earlier versions of this theory included him dying on 9/11, but the kids' ages at his funeral don't add up.
One theory that keeps popping up suggests Jack died in a car accident while doing something for Kate. She's the one who has his ashes and Fogleman did say it hits her the hardest.
A plausible version of this one could play out: Kate is partying with some of her new friends and calls her dad for a ride home because she's too inebriated to drive herself. Rebecca's out of town on tour, so he goes alone. Either because he had a drink himself before leaving or the fault of another driver, there's an accident and he's killed.
This would explain why Kate would feel responsible and have a hard time talking about what happened. It would also incorporate Jack's drinking problem.
Wrong Place, Wrong Time
Jack's a very good guy and maybe that's what led to his death.
Couldn't you see him trying to talk down a robbery or intervening in a domestic dispute in an attempt to do the right thing, only to have that end in tragedy?
It's a little more random than some of the options above, but it at least fits with his character's personality.
So far, we haven't seen the Pearson household in the present day. Could it have burned down with Jack inside?
As for why Kate feels guilty, maybe something she did started it? Or he ran back inside to save her, only to put himself in harm's way.
This would also help explain why Jack was cremated and would find a way to bring the fireman back into the picture, which you know the show would just love to do again.
Miguel Murdered Him
OK, this will NEVER happen, but it's still a theory that pops up all over Reddit.
Why'd he do it? To get Rebecca, of course.
Chrissy Metz told us we'll learn more about what happened by the end of the season, but will have to wait until next year to "see what's really going on."