News broke on Friday that Dermot Mulroney will leave NBC’s “Chicago Fire” in its upcoming 15th season. During a recent appearance at Flash Weekend Chicago Horror Convention (via People), Mulroney opened up about his exit. Popular on VarietyThe “My Best Friend’s Wedding” star explained that he only has one more episode left in Season 15, and then “they write the character off.” His exit is expected to come early in Season 15, which premieres on Oct. 7 at 9 p.m. Miñoso’s character, firefighter Joe Cruz, will likewise be written off in Season 15.