They're
suing armslist an internet bulletin board/broker over their role- whatever it may or may not have been- in facilitating a gun transfer to someone who then used it to commit murder. I had never been there before today, but today there are several admonitions to follow the laws, and a disclaimer that Armslist does not get involved in the actual transaction. And it's now the Internet Loophole.
The really terrifying precedent this would set is mind boggling. Any community center anywhere with a bulletin board for lost puppies, garage sales, and so on is now at risk. I can only assume the Brady Center isn't fond of more amendments than the second one.