More Celebrity News ►► http://bit.ly/SubClevverNewsFor fans of NBC's 'This Is Us' Jack Pearson's death has been a mystery since episode five. We know he died when the Big Three were teenagers and that Kate isn't ready to talk about it yet but not much else—and it's killing us! But die-hard fans have their own theories about what happened so right now, we're counting down the 5 most popular theories right here on LISTED. For More Clevver Visit:Keep up with us on Instagram: http://instagr.am/ClevverLike us on Facebook: http://facebook.com/ClevverTVFollow us on Twitter: http://twitter.com/ClevverTVWebsite: http://www.clevver.com Add us to your circles on Google+: http://google.com/+ClevverNewsTweet Me: http://www.twitter.com/rylandadams