changed my batter - alarm shut down car, please help

hi... my buddy has a honda accord 1990 and just replaced his battery. but now when he hooked everything back up... it won't start because the alarm armed and has shut everything down. any suggestions? is there a way to reset it?

what kind of alarm does he have? I find that odd. I have owned many alarms and that has never happened to me.

i had to re connect my alarm after i changed my battery, it kept going off. try that.

When I reconnect the battery my alarm is on, but I just push the button and it disarms..