After 12 seasons, actor Thomas Gibson was fired from Criminal Minds, with FBI Special Agent Aaron Hotchner written out of the series. The Criminal Minds FBI cast revolved fairly often, with actors choosing to leave the long-lasting show behind to pursue outside interests, but this wasnt the case for Thomas Gibson. Aaron Hotchner wasnt officially written out until season 12, episode 6. Hotch left Criminal Minds because the character went into the Witness Protection Program after a serial killer stalked his son. He eventually chose to be a full-time father to Jack rather than return to the BAU.

https://screenrant.com/criminal-minds-thomas-gibson-fired-hotch-exit/