Pontiac Repair: Cant get my radio to work and there is now a constant thumping from my driver side speaker even when the car is turned off

Question
Car info up front:
2005 Pontiac Grand Prix with the 3800 engine not supercharged
Have an after market radio ( installed by Best Buy)

My key got stuck in the ignition at work and killed my battery. after jumping the car to get it running the radio began flashing on and off and there was a thumping coming from my driver side speaker, that doesnt quit even after the car is turned off, the only way to get it to quit is to pull the radio fuse. i have since checked the fuse on the back of the radio, i dont think there was one on the gmos unit , the radio fuse in the box and the RAP relay. not sure what else to do.

Answer
Hi John:

sorry for the delay there was an issue with allexperts I never got your question till today.
does this have the factory radio in it and if so is it an monsoon radio system? could be a bad amplifier. when you jumped it may have screwed up the amplifier and or the radio. an monsoon system has an amp and that vintage they were really voltage sensitive so a jump start could have damaged it. with out seeing it I can't tell you for sure.