Has anyone experienced this or may know what is causing this?

The other day my '02 X5 4.4 was dead so I jumped the battery, drove it for 20+ minutes, and parked it. Later that night my factory alarm went off, I went out to turn the alarm off, and everything seemed dead....door locks, etc. Then, the alarm starting going off (battery must be OK) & I could not turn it off.

My battery is about 3 yr.s old now and I replaced the alternator about 3 yrs ago also.

This sounds electrical, any ideas?

Thank You