Well, he was panicked and had no clue what to do. In a similar situation, I think most people would want to just get out of there. Its understandable. I think it'll be interesting to see what really happened. I just hope it isn't something contrived and stupid as has been mentioned in other posts here.
Something I noticed was that when he runs out, the door is locked behind him. He has to break in to open it, then runs out. Later, when the cops show up they're able to open the door as it isn't locked. This kind of makes you wonder, did someone lock the door behind Naz? The door doesn't seem to autolock. That locked door is probably the biggest clue that it's not him, if it's not an oversight by the writers.
And yeah I know he's panicked, but every innocent person who comes across dead bodies usually immediately reports them to 9-11. They don't spaz out like that, and that's just adding fuel to the fire if he's truly innocent. Calling the cops and just being honest (probably with a lawyer present) is the only right play here, as you have to understand that if they charge you then they're letting the real killer walk. Cops leave you in a cold interrogation room for hours, making you uncomfortable, and then come in with a partner (showing power) and then go from being very polite to being incredibly blunt very quickly. This is all to try to make you break down, slip up in a lie and then confess once you're caught lying. They really tend to rely heavily on their instincts. If you're honest and they believe you, they may look at other possibilities, however remote.
If I were a cop, given the breaking and entering and him trying to dispose of the knife... he's beyond Casey Anthony/OJ level guilty to me and I'd probably never change my mind or consider another suspect. That's why informing law enforcement yourself that there's a dead body is so important, yeah there's a lot of evidence but at least you're not actively trying to deceive them from the get-go by hiding shit, like Casey Anthony. Speaking of her, I recall that they found some evidence on her computer after her exoneration which pretty proved she was guilty beyond
anydoubt.
Casey Anthony detectives overlooked Google search for "fool-proof" suffocation methods, sheriff says - CBS News
WKMG reported that sheriff's investigators overlooked over 1,200 entries including the suffocation search from the computer's Mozilla Firefox browser, which was most commonly used by Casey Anthony. Investigators also pulled 17 vague entries from the computer's Internet Explorer browser.
Whoever conducted the Google search looked for the term "fool-proof suffication (sic)" and then clicked on an article about suicide that discussed taking poison and putting a bag over one's head, the station reported.
I just think you have a much better chance being completely honest and upfront about the events of the night, than you do actually getting away by hiding evidence and them not tracking you down. Any decent detective would have been able to track him down like 95% of the time considering what's already present at the scene. If they don't, if he's ever arrested (for anything) and his prints/dna go into the database, he's fucked. Once you're fucked, you're really fucked.