Derrick Gibson has left Chicago Fire (here's how he was written out)

Derrick Gibson (Rome Flynn) had lots of potential. The character was brought in as a replacement for Blake Gallo (Alberto Rosende), and while he displayed a similarly heroic streak when it came to fires, he struggled to maintain control when it came to his emotions.

Gibson struggled to connect with the rest of Firehouse 51 during his tenure, which came to a tragic but unsurprising end in the episode "All the Dark." He seemed as though he was someone who liked to play things close to the chest, and be less social than his predecessor, Gallo, but when he opened up to Sam Carver (Jake Lockett), the extent of his trauma became clear.

Gibson began abusing prescription drugs

Gibson was an amateur boxer who accidentally killed a man in the ring, and the regret, coupled with a similar incident involving a high school basketball player, resulted in him coming apart on the job. He struck up a genuine connection with Carver, but it proved to be a double-edged sword, as Carver knew to keep a special eye on him.

Sure enough, Carver noticed that Gibson was abusing prescription drugs in "All the Dark", and tried to confront him about it before one of the higher-ups did.

Related: Why Chicago Fire's new medic was fired

Carver emphasized with the rookie firefighter, but reminded him that he wasn't the only one who had "demons" to contend with, and told him to pull himself together if he wanted to keep his job.

Unfortunately, the tough love didn't take effect. Gibson was angered by the interaction, and promptly punched his locker after Carver left. The punch damaged his hand, which in turn triggered a panic attack. Stella Kidd (Miranda Rae Mayo) eventually found Gibson trying to calm himself down in the bathroom (she did so by following a trail of blood from his injury).

Gibson told Kidd he needs to leave 51

Gibson was a defeated man by the time Kidd found him, and his last words were appropriately heartbreaking:

"I thought I pulled it together. I need to get out. I need to go."

That's all she wrote. Gibson left Firehouse 51 for good at the end of the episode, closing the door on the show's latest firefighter, and opening the door for the next one.