97 jetta locked down

hello, sold my 97 jetta to my brother. he set the alarm off, since then, the alarm light blinks at the door, locked or unlocked, the keyless doesn’t work at all and the car will not even try to turn over. try to reset the anti thief with the key at the drivers door, but nothing, any ideas? unhook battery? any help would be welcomed, thanks, mark

What does the owner’s manual say about this?

I’d say it’s your brother’s problem. He set off the alarm.

This is why I don’t like automobile security systems.

the manual just says the system has it shut down and to reset it with the key to the drivers or passager door…but that didn’t…thanks for the reply