From Firehouse 51 Rookie to Fan Favourite

When Charlie Barnett first stepped onto Chicago Fire in 2012, his character Peter Mills arrived as a determined firefighter candidate starting at the bottom of the ladder. He wanted to prove himself, honour his late father, and earn his place at Firehouse 51. Fans watched him rise through the ranks with grit and heart, making him one of the standout names in the show’s early years.

Mills began on Truck 81. Over time, he moved to Rescue Squad 3 under Lt. Kelly Severide, then switched roles again after a serious injury forced him to join Ambulance 61 as a paramedic. Even then, he kept fighting to return to frontline rescue work. He eventually made it back to Rescue Squad before his exit. Along the way, he also had a complicated romance with Gabby Dawson, adding emotion and heartbreak to his journey.

For many viewers, Mills represented the spirit of the show: a rookie becoming a real hero through persistence and loyalty.

A Departure That Shocked Fans

Given his importance, it was a blow to audiences when Mills was written out in Season 3. The character left Chicago to run a restaurant with his family. Some fans hoped it was temporary. But behind the scenes, Barnett was dealing with the emotional impact of being let go.

He later revealed he had no idea Chicago Fire would become such a massive hit. “It was a behemoth I never saw coming,” he told Digital Spy. His gratitude was clear, but so was his pain. “I was really sad to be let go,” he admitted. “It broke me for quite a long time.”

Barnett Says Goodbye—But Fans Never Did

Barnett also shared a message on Twitter at the time, saying he would have stayed if it were up to him. “If I had my way, I wouldn’t be leaving,” he wrote, calling his experience on the show “beyond amazing.” More than 60 episodes across Chicago Fire and four appearances on Chicago P.D. made him part of One Chicago history.

Fans still talk about his exit and often mention Peter Mills as a character they would welcome back without hesitation.

A New Chapter After the Flames

Leaving Chicago Fire was painful, but Barnett moved on to major roles in hit series including Orange Is the New Black and Russian Doll. His career proved that one closed door can lead to something unexpected and bright.

Still, for many fans, Firehouse 51 will always have a space waiting for Peter Mills.