Why is Şahin in prison in Uzak Şehir?

In the 17th episode of the series Uzak Şehir, which aired on March 10, Şahin enters prison. The events leading to Şahin's imprisonment begin when Kaya abducts Zerrin, who was wearing her wedding dress on her wedding day.

When Kaya abducts Zerrin, both Zerrin's family and the family of the groom-to-be, Sedat, go after Kaya and Zerrin. Zerrin and Kaya go into hiding but are caught a few days later.

In the middle of a field, guns are drawn. Sedat's father, Mahmut Ağa, points his gun at Kaya. Realizing that Mahmut is about to shoot Kaya, Şahin lunges for Mahmut's hand. The pistol is right between Mahmut and Şahin... Şahin tries to take the gun, and Mahmut refuses to let go. And the gun goes off. Mahmut collapses to the ground. Immediately after the gun goes off, the police arrive. Şahin is sent to prison for killing Mahmut.