I would try pushing the unlock button inside the car. If the locks lock/unlock let us know. If this doesn't work.
Check fuse # 9. If your replace fuse #9 and it opens again then.
Has the siren ever been replaced? If not try unhooking it and let us know. It is located under the windshield wiper cowl. You will need a small puller to get the windshield wipers off.
There is a great thread on this forum just search siren.
Next, Have you checked the passenger side trunk well under the black molded foam for water? You can slide a piece of printer paper down between the black foam piece and the far right passenger side and if it come up wet you know. There is a great thread for this as well search headlight headache water in trunk.
This is where I would start please let us know what you find.
I hope this helps get you started. If you have more questions please ask.