Spend 24hrs or something outside of town. Then go back. They'll be less aggressive and go "hey, I remember you...". You're still wanted, but you can bribe them off or pay your fine instead of having a sword stuck down your throat.
I think the aggression happens if someone sees you perform a crime, but you run away before a guard catches up to give you his arrest speech. When you come back next, they default to DIE!!
Talking about die, I killed 2 dragons today. One of them crept up on me and just landed right in front, then started breathing fire. The other one was sleeping.
They took 7 and 2 seconds to dispatch respectively.
Oh. Yeah.