Hello,
I just returned back to US after 2 months in Europe.
My friends arrived four days ago and they tried to drive my Camry. As you might expect the battery was down. Anyway, they recharged it and they were driving the vehicle successfully for two days.
However, next day they tried to start the car, but instead the gauges shaked a little bit and the alarm went off. Now the alarm goes off everytime we open the door.
Some info about the car:
Toyota Camry '94 V6 XLE, I own the car for almost a year. This never happened before (but we had a battery problem once).
I have no idea whether it is a factory or aftermarket alarm. I would say it is an aftermarket one because Toyota itself would make it more fancy

There is a red LED between the steering wheel and driver's door. It used to be always on but now it is blinking.
We have no remote, just keys. Moreover, I am not sure if they are original.
I had no idea that the car has an alarm, I thought the LED is just fake.
Thank you very much for your help.