'This is Us' episode 17 spoilers
Cast member Justin Hartley (R) and Chrissy Metz (L) answers questions during the panel for "This Is Us" at the NBC Universal Television Critics Association press tour in Beverly Hills, California, US, August 2, 2016. Reuters/Phil McCarten

The Feb. 21 episode of "This is Us" finally revealed a key to the puzzle about Jack Pearson’s (Milo Ventimiglia) unexpected death years back. While fans seemed to be heartbroken at the character’s untimely demise, the little bit of when, how and why that uncloaked in the season’s last episode came as some sort of a relief. Nonetheless, they are yet to know what exactly killed off Frank and under what circumstances.

Actor Justin Hartley, who plays Kevin in the NBC comedy drama series, dropped by the US Weekly’s NYC headquarters on Feb. 22 to discuss the show. Here’s what has been revealed during the discussion.

"You'll never guess it," the 40-year-old told Us Weekly of Jack's fate. "It's unexpected and it's extremely heartbreaking and sad and deep and moving and, ugh, it's painful,” Hartley added. “It'll stay with you.”

It was divulged last month that Jack died when Randall, Kate and Kevin were just teenagers. Given that the flashback funeral scene didn’t reveal much, fans took to prophesising theories of their own on how Jack died.

The NBC comedy drama "This is Us" first aired on Sept. 27, 2016 and the show has since seen a viewership influx of almost 10 million, i.e. from 4.9 million to 14.5 million. The current viewership rating stands lofty at 2.8 in adults in the 18-49 demographic.

What makes the series more preferable is the emotional drop that has been added, to the otherwise a comedy, for dramatisation purposes. Viewers are used to stocking up on tissues, it has been said. The last episode titled “Memphis” also saw Randall’s biological father, William Hill (Ron Cephas Jones) succumb to his stage IV diagnosis.

Hartley further talked about how he watches the emotional episodes. It’s either live or ahead of time on the sets, he said. “Sometimes I'll watch the New York feed if we're in LA. Whenever I'm tweeting the show I like to have watched it once before so I can [fully enjoy it].” The actor added that he likes watching his fiancée Chrishell Stause watch it.

Hartley’s on-screen romance, however, isn’t as sound as the real-life one. His character Kevin can be seen trying to win his ex-wife Sophie (Alexandria Breckenridge) back. Kevin had previously cheated on her which led Sophie to end the marriage.

"I think he's serious about getting her back and I think unfortunately good people do bad things sometimes," Hartley told Us Weekly. “He's trying to convince her that he's changed so yeah, I think he can earn her back. I think it's going to take some time.”

“This is Us” currently airs on Channel 10 in Australia. In the US, the show airs on the NBC network. The next episode titled “What Now?” will air on March 7, 2017.