Buzzing sound coming from under dash and goes away when you press brake

[Remington8904]

Hey guys thanks for your help in advance! My sister owns a 2004 Explorer Limited. Today she stopped and got gas. Before she stopped the truck was running fine. She went to start the truck after getting gas and it had a dead battery. She then put the car into nuetral to push it off to the side. They tried to jump start the battery and that did not work. When the tow truck got there they attempted to put the car back into nuetral, well it would not budge out of park. Well they tried to jump the battery again to put the truck into nuetral but had no luck. When they got it home I got to looking at it. When the cables are connected to the battery, there is a loud buzzing sound coming from the driver side dash by the fuse box. When you press the brake pedal, the sound goes away. They truck will not do anything when trying to start it, no lights or radio at all. When I placed jumper cables on the battery, the buzzing noise became louder, but would still go away when you press the brake pedal. I then removed the #1 fuse from the fuse box under the hood and that made the buzzing stop. That seemed to help give the battery a little more juice. I tried to start the truck again and the radio lights and glovebox lights started to come on and off as if it was running off a turn signal switch of some sort. The truck did not turn over at all.
I have searched everywhere but could not find anything with the same symptoms online. Thanks again everyone!