‘9-1-1’ Star Oliver Stark on Buck’s Five-Alarm Heartbreaker News (VIDEO)

Evan “Buck” Buckley (Oliver Stark) is the latest character to have his origin story told on the first-responder drama — and the daredevil firefighter’s past is a heartbreaker.

“The main thing we learn is that Buck has never quite belonged in his family,” says 9-1-1‘s Stark (above). “And not just his immediate family, but even his found family [within the Los Angeles Fire Department]. There’s always been something missing.”

That becomes clear when Buck’s parents (Gregory Harrison and Dee Wallace) come to town to visit his pregnant sister, Maddie (Jennifer Love Hewitt), and a long-buried family secret (depicted in flashback) is revealed.

“It’s quite earth-shattering news for him,” Stark says, adding that the development forces Buck to look at his potentially self-destructive addiction to risking his own life for others. “This [news] isn’t going to completely change who he is. I don’t think he’s ever going to stop running into fires to help people, but he’s going to do it a bit more [responsibly].”

Check out an exclusive clip above to see the 118 getting ready to head into one of those fires.

Buckley Parents 911 Season 4 Episode 5 Dee Wallace Gregory Harrison

Jack Zeman / Fox

9-1-1, Mondays, 8/7c, Fox