Break way switch and locked up brakes

[Mikendebbie]

...not on my unit - it was the guy next door.

He had a new Rockwood bumper tow and nice Ram dually. He was hitched and ready to go. He pulled out a few minutes before me and I could see his wheels were locked up and making horrible noise. I flagged him down figuring it was the break-away pin not being inserted correctly, and it was completely out and hanging there. I clicked it back in for him - but the brakes would not release.
We were up against check-out time and I had to leave, plus I saw another guy coming over to help out - but I had no idea what to do to get the brakes to release. I had never been in that situation.

What is the answer?