This Is Us will soon show the events that led to Jack Pearson's death, and all fan speculation regarding how it went down will finally be laid to rest. With that said, here are a few theories we have regarding how Jack lost his life and how his death connects to some of the other clues fans have been teased with prior to the reveal:
Jack Died In The Fire After Going Back To Save The Dog
This theory is the front-runner because a lot of the plot supports it and it feels like the most obvious and realistic scenario that could unfold. Many fans of This Is Us had already theorized Jack met his end saving someone from the fire, and Kate's recently revealed apprehension of dogs in the present could confirm this. Fans know Kate blames herself for the death of Jack, and while the teaser for the next episode showed Jack readying himself to rescue his daughter, there was no mention of the dog, who was last seen sleeping downstairs.
We know from a scene in an earlier episode that took place at Miguel's following the incident the dog survived. We also know Jack would go to any length to keep Kate happy, so it isn't hard to imagine him entering the burning building once more if she was upset. In this scenario, the dog found its way out either before or with the help of Jack. Then Jack, either unaware of where the dog was or unable to maneuver his way out of the house, perished in the fire. Kate, unable to cope with the grief, blamed herself and avoided dogs in the future due to the trauma of the event.
Jack Was Rescued From The Fire, But Is In A Coma And Died Later
This death theory stems from a scene from Season 1 in which Kate flashed back to Jack's funeral. In that Season 1 scene, Kevin did not have his boot on, which meant his leg is healed by the time Jack is buried. Now, this could be a continuity error on the part of This Is Us, or Kevin could also be close to getting his cast removed, but there is another option. What if Jack was rescued from the fire, but he's unconscious due to smoke inhalation?
Rebecca had a bunch of Jack's belongings in bags presumably from a hospital back when the fire flashback was first shown, but that doesn't necessarily mean Jack is dead. If Jack were in a coma for weeks and didn't die until Rebecca made the decision to pull the plug, it would certainly explain why Kevin's leg is fine by the funeral. This theory is also supported by the fact that everyone in the aftermath fire flashback didn't outright say Jack was dead, which could mean he's alive, but in bad shape. It would definitely be a sad direction for This Is Us to head considering we all know what eventually happened, so let's hope that the show doesn't go this route.
Jack Died In The Fire After Going Back In The House To Save Kevin
Kate blames herself for the death of Jack, but she doesn't seem to be the only Pearson that feels that way. The prior episode of This Is Us showed Kevin plans to make amends with his father to complete his list of names he made following rehab. Kevin may be referring to a fight he and his father had the night of the fire, but what if Jack went back into the house to save Kevin unaware of the fact that he was staying at Sophie's that night? Kevin would definitely feel some responsibility for Jack's death if that were true, although a couple things would have to be revealed in the upcoming episode for this to work.
For example, Rebecca knew Kevin was staying at Sophie's, and while she never told Jack in the episode, she certainly can in the family's escape. If Rebecca is unconscious or something of that nature, Kate (who also may not know where Kevin is) could be the one who realized Kevin and the dog were missing and informed Jack. This allows both Kevin and Kate to feel some responsibility for what happened and could be why Kevin feels the need to make amends with his father.
Miguel Killed Jack In An Elaborate And Convoluted Plot Twist
Jack appeared to die as a result of the fire; what if someone was there to ensure he never made it out? What if Miguel knew the Pearson home caught fire because he rigged the Crock-Pot to malfunction and burn down the home? Just imagine: with the plan in place, Miguel then hid in the house and waited for the flames, hoping to be the hero who saved Rebecca and the children while Jack died in the fire.
Unfortunately, Jack proved more heroic than his former best friend imagined and managed to get everyone out of the house. Defeated, Miguel sat inside the burning home realizing his dream of becoming Rebecca's lover years later would never happen. Suddenly, the door flew open and Jack came in searching for something at Kate's behest. Miguel wasted no time and subdued his former friend and left him for dead so he could get home and take a shower. This twist, while unlikely, would turn This Is Us into a thriller and certainly keep things exciting going forward. No one really asked for that to happen, but This Is Us has to keep things fresh after Jack's death reveal!