What is the right ruling?

[mpeterson_1]

I think this is what's called a "false multiple foul" if I'm not mistaken. I've never called one of these, but in this case, if you don't think B2's contact caused A1 to foul B1, you have to call both on the double whistle. IMO, the only way you have one foul here is if you are the only whistle on the play AND/OR you deem the first foul the cause of the 2nd.