In my novel, Matt's girlfriend Ella gets kidnapped and Matt is held responsible by the kidnappers. As it wasn't for ransom but as a revenge of something Matt did. And then Matt storms into my MC's office and there he explains how much innocent he is and starts telling why there is no reason for Ella to be kidnapped as he is basically a very nice guy.

At this point how do I introduce Matts back story in a show not tell the way? Like instead of Matt saying, "I haven't done anything wrong", how should the backstory come here?

Do I have any option here other than Matt telling his own back story?