A mysterious group operating under the name "Listen to the Children" called out four members of Minnesota's congressional delegation Monday on their positions on gun control measures and donations from the National Rifle Association.

In a full-page ad in the Star Tribune a week ago, the group asked the entire Washington delegation if they would introduce, cosponsor or vote for legislation to ban the manufacture and sale of high-capacity magazines for firearms, and if they would return any donation from the NRA and its affiliates and refuse to accept future NRA donations.

That ad came just two days after 20,000 Minnesota students and adults rallied at the State Capitol, joining hundreds of thousands of protesters in D.C. for the March for Our Lives event. The student protesters are pushing for stricter gun control laws in the wake of the Parkland, Fla., high school shooting that killed 17 teens and staff members in February.

On Monday, the nonprofit placed another full-page ad, saying it received "yes" responses from Sen. Amy Klobuchar, Sen. Tina Smith, Rep. Tim Walz, Rep. Betty McCollum and Rep. Keith Ellison — all Democrats. The ad said that Rep. Erik Paulsen, a Republican, was the only one to respond "no" to both of the group's questions, but a spokesman for Paulsen's office said their organization never responded to the ad. Rep. Jason Lewis and Rep. Tom Emmer, both Republicans, and Rep. Collin Peterson, a Democrat, also didn't respond to the group, which stated in the ad that it considered a lack of response as "no" answers.

It's unclear who exactly is behind the ad.

The group published a Minneapolis P.O. box address, and a reporter's questions sent to the group's P.O. box weren't answered. According to public records, the nonprofit filed with the state Secretary of State's Office on March 9 and listed a St. Paul business address and CT Corporation Systems Inc. as a registered agent.

The nonprofit also listed Ellen Durkin, a paralegal at the Minneapolis-based law firm Gray Plant Mooty, as the incorporator, but the firm said it won't discuss or provide any information about a client due to attorney confidentiality.

In response to a reporter's request, the Star Tribune advertising department, which is separate from the newsroom, declined to identify who paid for the ad, citing confidentiality in ad agreements.