Boxer was protecting his boss' son Oriol, whom Clint suspected of having killed Axel. ... He had burned down the club Axel named after Kika, and hated Axel for sleeping with both his sister and mother (to whom Oriol was incestuously attracted), but he didn't kill him.

Who killed axel?

Axel was murdered by his best friends, Anna and Marcus.

Both Boxer and Zoe instantly gravitate toward Marcus (Daniel Mays), Axel's best friend. Their instinct is spot-on.

What happened axel?

Axel is still not dead though, leading Anna to get out of the car and hit him before stabbing him, finally killing him. In the present day, Anna tells Zoe she killed Axel because she was worried that Marcus would find out about the affair.