Why did Peter Mills leave Chicago Fire? Explained

Chicago Fire is a long-running series that premiered on NBC on October 10, 2012, and is currently in its thirteenth season. The series covers the trials and tribulations of the fictional Firehouse 51 of the Chicago Fire Department.

This show is the first series in NBC's One Chicago franchise, consisting of procedural dramas covering the full spectrum of Chicago's law enforcement and emergency services. Other series under the franchise include Chicago PD, Chicago Med, and Chicago Justice.

Being a long-runner, Chicago Fire has had its share of cast turnover over the years. One notable departure has been Charlie Burnett, who plays Peter Mills. When speaking to TV Guide in April 2015, executive producer Matt Olmstead explained that Peter was being written out of the show because his character arc was complete, and they wanted to make room for new characters.

Charlie himself recounted his departure to the Sarasota Herald-Tribune. He claimed that he was told his exit wasn't personal or related to his acting abilities but rather a result of writers feeling Peter had reached a plateau, and there was not much else for the character to do.

Speaking to Digital Spy, he elaborated:

"[The show] was a behemoth that I never really saw coming. I was thankful to be a part of it. I really was sad to be let go. It broke me for quite a long time."

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Peter Mills left Chicago Fire in season 3

Peter Mills was introduced to Chicago Fire in season 1, as a Firefighter Candidate. He was the son of Henry Mills and sought to follow in his father's footsteps as a member of the Rescue Squad. Due to his father's career record, then-Battalion Chief Wallace Boden and Lt. Kelly's father, Benny Severide, were familiar with him.

Peter found himself in the middle of a spat between two lieutenants upon joining Firehouse 51, as there was still some lingering tension and animosity because of Andrew Darden's death a month back.

As he was a newbie, he was hazed by CPD veterans who called him by his full name instead of just his last name, as protocol suggests.

By the end of season 1, he was considering transferring to the CPD because he didn't get a promotion, but he eventually decided against it. He would subsequently be promoted to Squad 3. At the end of season 2, Peter suffered a leg injury that put him out of commission. After returning to work, he continued to have health issues, with him complaining to Kelly Severide about dizziness.

During his medical appointment, Peter learned he was no longer fit to continue as a firefighter, prompting him to switch to paramedic training and start working alongside Sylvie Brett.

By the end of Chicago Fire season 3, Peter was written out of the show after discovering that his paternal grandfather owned a restaurant in North Carolina, which Peter's family had not inherited.

Previously, Peter's family owned another restaurant that had burned down. Therefore, after finding out about his grandfather's restaurant, his mother and sister were very excited about making a move. However, Peter was reluctant as it would result in his retirement from the CPD. Eventually, he decided to leave and be with his family.

When speaking to TV Guide, former executive producer Matt Olmstead had this to say about Pete Mills's departure:

The hardest part of this job is when you feel it's the right time to make cast changes. It was solely based on bringing in new people for new stories. Otherwise it turns into a clown car. You have affection and admiration for [your cast], so you keep everybody, but it's at the detriment at being objective and making some tough calls in terms of storytelling."

When speaking about how Pete Mills was written out, Olmstead elaborated that his character arc had him conflicted about following in his late father's legacy while still doing right by the family he left behind.

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Chicago Fire airs Wednesdays at 6 pm PT on NBC.