Facebook plans a briefing for state AGs on Thursday

"Consumers have a right to know how their information is used – and companies like Facebook have a fundamental responsibility to protect their users’ personal information," Schneiderman said in a statement. "Today, along with Massachusetts Attorney General Healey, we sent a demand letter to Facebook – the first step in our joint investigation to get to the bottom of what happened."

Facebook's response: “Attorneys General Healey and Schneiderman have raised several important questions," said Will Castleberry, Facebook's VP of State and Local Policy, in a statement. "We appreciate their attention to this matter and look forward to responding.”