Flashing lights

I recently purchased a 2000 blazer. The other day I got in. When unlocking the doors the horn, lights started flashing, and dome light was staying on. If I use the dome override button engaged it will not do this. It does it when you are entering and exiting the blazer. When purchasing the blazer it did not have a keyless remote just one key with the it. How do I shut this off and what do I need to do.

This is all I could find from the owners manual.

Here’s how to avoid setting off the alarm by accident:

If you don’t want to activate the theft-deterrent
system, the vehicle should be locked with the door
key after the doors are closed.

Always unlock a door with a key, or use the remote
keyless entry transmitter. Unlocking a door any other
way will set off the alarm.
If you set off the alarm by accident, unlock any door
with the key. You can also turn off the alarm by
pressing UNLOCK on the remote keyless entry
transmitter. The alarm won’t stop if you try to unlock
a door any other way.

I have tried that and it seems that even if the doors are not locked and you open one the system goes off. I am not able to use the power locks even if I use the key to open the doors.

I have tried that and it seems that even if the doors are not locked and you open one the system goes off. I am not able to use the power locks even if I use the key to open the doors.

Well I'm not sure really what to do,but heres a link to buy a new keyless entry remote cheap http://www.originalkeyless.com/category.sc?categoryId=6

Thanks