For the first seven seasons of the NBC drama Chicago Fire, Yuri Sardarov played fan-favorite firefighter Brian "Otis" Zvonecek. But in the Season 8 premiere "Sacred Ground," Otis died from injuries sustained while fighting a fire at a mattress factory. Years later, fans continue to mourn his loss.

Created by Michael Brandt and Derek Haas, Chicago Fire premiered in 2012, following the lives of firefighters at the fictional Firehouse 51. Sardarov's character was one of the original first responders and was a source of comedic relief in every season of Chicago Fire, including a subplot where he dated the half-sister of Taylor Kinney's character Kelly Severide. Otis' death shook up the show and reminded viewers that, despite many of the main cast continually emerging alive after cliffhangers, the perils facing the firefighters were deadly.

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How Did Otis Die on Chicago Fire?

Otis (played by Yuri Sardarov) lays in a hospital bed on Chicago Fire

The firefighters battled a fire at a mattress factory in the Chicago Fire Season 7 finale "I'm Not Leaving You." Chaos erupted when a boiler exploded, leaving everyone's fate up in the air. The Season 8 premiere picked up immediately in the aftermath. While attempting to evacuate, Otis was trapped in the blaze and got a distress call out to his colleagues. Unfortunately, he suffered devastating injuries and was unable to exit safety with the other firefighters.

His team rescued him and rushed him to the hospital, where he died by the side of his best friend and roommate Joe Cruz (Joe Minoso), after telling him in Russian that "Brother, I will be with you, always." It wouldn't be until three months later that Cruz learned the translation of Otis' last words. His death hung heavily over the team at Firehouse 51, and while mourning their fallen teammate, the firefighters erected a memorial to Otis, ensuring his impact would never be forgotten.

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Why Yuri Sardarov Left Chicago Fire

Chicago Fire's Matthew Casey (played by Jesse Spencer) moves through the burning mattress factory

In an interview with TV Line, Chicago Fire showrunner Derek Haas revealed the writers wanted to shake things up after several cliffhangers in which the main cast had miraculously survived. "We gotta put some teeth back into the show, and we gotta show that the dangers are real," he said. The writers knew that in order to reintroduce an element of greater danger to the series, a character was going to have to die.

Originally, Darren Ritter (Daniel Kyri) was slated for the chopping block, but the character was too new to the series, and Haas said the emotional toll of the death would only be felt if it was a longtime cast member. "For it to be a real surprise, you need it to be a core cast member. We thought that Yuri affects everyone in the house as well as fans," Haas told TV Insider. "I had seen a memorial at an LA firehouse, and I thought that's something we've never done before. I was thinking how could he be remembered, so I had the memorial as the ending in my mind and worked backward from that."

Losing Otis was tough for fans, especially after everything that he'd endured in previous seasons. His demise had a lasting impact on Chicago Fire, especially for his best friend Cruz -- who'd go on to name his child Otis. Most significantly, however, Otis's death challenged the writers to bring a realistic sense of danger back to the series.