Detroit police chief Ralph Godbee resigned Monday after embarrassing news surfaced about his sexual relationship with a subordinate.
During a news conference, Mayor Dave Bing said he didn't force the chief to leave but said it was the "right decision", reports AP.
"He was very contrite, I think embarrassed," Bing said.
"He felt he had let me down. He felt he had let the department down. He felt he had let the citizens of Detroit down. We're not perfect individuals, and a lot of us make mistakes. This one was very costly."
Godbee was revealed to be having an affair with fellow officer Angelica Robinson, who worked in the internal affairs department.
Robinson became the subject of headlines when she posted a photo to her Twitter page of herself with a Detroit Police issued 9 millimeter Glock handgun in her mouth after she believed Godbee was with another woman.
Detroit's Fox2 reports that the gun has since been taken away as Officer Robinson undergoes psychiatric evaluation.
Godbee was placed on a 30-day suspension last week pending an investigation into claims by Robinson's attorney that she wanted the relationship to end and Godbee did not, reports Fox2.
The Los Angeles Times reports that the chief, who is separated and has filed for divorce, has not publicly commented on the scandal and made no mention of it in his resignation letter.
Godbee has been a member of the Detroit police department for 25 years and spent the last two as chief.
AP reports that assistant Chief Chester Logan, who took on Godbee's responsibilities during the suspension, will serve as interim chief until a new one is hired.