The entire 'Bomb in the Mailbox' scenario is ABSURD
Okay - what's easier? Plunking Harry with a rifle with a silencer from a rooftop - or having to plant a bomb in a public mailbox???
Think about it. These ROOKIE cops would have to have a pretty vast understanding of plastic explosives. That's not something taught to traffic cops in the Academy. Plus, each mailbox (Early and Harry's) are in public areas - Early's is right on the street for crying out loud. They would have to dismantle the mailbox, pull out their bomb, carefully attach the bomb, then reattach the mailbox - all with no witnesses noticing them.
Yeah - I know it's a movie - and the bomb sets up a neat ending - but when you think about it - there's much more efficient ways to kill a single person.
Plus - there's the obvious issue - what happens if the mailman delivers the mail before Early and Harry get home, but after the bomb was planted?? I'll tell ya -
BOOM! Bye Bye mailman (and bystanders)
Post is MY OPINION. Don't look for spelling/grammar errors as this isn't a PhD Thesis.