[RWebb]

Yes, of course, call the police! Do it right now.

You most likely were trespassing - depends on the state & what posting or fencing is required, but despite some of the ignorant comments above, it is completely illegal to shoot at anyone for trespassing on land anywhere in the US.

Any penalty for your trespass will most likely be minimal.

Anyone crazy enough to shoot at somebody in an open field like that needs a little jail time to cool them off.