spoilers:end of spoilers
He took the shirt probably because he's going to be doing the punishing from now on, but in his own Daredevil way. He also came to the realization that he killed the store thief, therefore probably no mystery there but who knows. The thing that resonated with me the most was when Det. North hung the phone up on Fisk. The last person he wanted to get friendly with was Fisk and he's now probably started to realize what a mess-up he's made due to his over zealousness in bringing in Daredevil. Coupled with the fact that Daredevil handed over Frank, we may just see a Daredevil/Cole team-up in bringing down Fisk.