I may have goofed a bit

So I've played this game for like 10 hours and I thought I solved the murder case.

I found a gun at the crime scene with the victims handprints and someone else's, same bullet wound and calibre that matches the gun plus it was stashed away under a chess kit. Spent quite a while tracking him down, found connection to the workplace and he was in the same building. Footprints found in the murder scene too was something to go off of and a signature on an email.

I was proud and ready to take in this scumbag, went to city hall and got some cuffs and a club (to apprehend him). I waltz over to this dirtbags den, ask him a few questions and he's all cagey with details not even accepting bribes. I bash his head in and cuff him, take his prints and Footprints and they match perfectly. I scrounge his place looking for other evidence as well as any valuables (he probably stole them) so I can sell them for my extra payment.

Go to turn in the evidence.... it's all wrong.... i just beat the shit out of a random guy that knew the victim and robbed him because of a bad lead.... how the fuck did I get it so wrong?