trying to jump battery lights flash and horn blows

It's probably your alarm system that's going off. When the battery died, the car's alarm system assumed that someone is tampering with the battery or had disconnected it in order to break into the car. Here's what you can do hook up the jumper cables. The horn will start to blow. As soon as it does, using the key fob, lock and then unlock the doors or basically whatever you usually do to shut off your alarm. once you've disabled the alarm go ahead and try to start up.

You can also put your key in the door and lock and unlock a couple of times. Worked great!

Another way to stop the horn from blowing, open fuse box and remove horn fuse. Connect battery , start car and reinstall fuse. Problem solved

When I was trying to remove cable of negative terminal of battery I forgot to lock car by remote then suddenly I touch negative cable to terminal of battery and looked car but it different sound but after charging battery when I first connect positive and then negative it started blowing siren..so I didn't connect negative terminal because when I m trying to connect negative terminal it started siren like as a someone trying to open door with different keys or say stealing..how can I resolve this problem?