BOSTON (AP) – Republican U.S. Sen. Scott Brown and Democratic rival Elizabeth Warren challenged each other to provide more details about their work histories on Wednesday, the day a second video surfaced showing Brown speaking to supporters while war whoops can be heard in the background.

Late Wednesday, a spokeswoman for Brown issued a statement saying that he regretted that members of his staff were seen in an earlier video shouting war whoops and performing tomahawk chops, an apparent reference to Warren's claims of Native American heritage, and that they have been given their “one and only warning that this type of conduct will not be tolerated.”

Earlier in the day, Warren faulted Brown, a lawyer, for failing to release the names of his clients during his years of public service, including the time he served in the U.S. Senate and Massachusetts Legislature.

“As I understand it, he has been in public services now for 25 years and had never released the name of a single client,” Warren said during a campaign stop in Boston.

Brown reported earning more than $147,000 from his law firm from 2008 to 2010.

Brown sent out a letter earlier in the morning calling on Warren to provide an accounting of her corporate legal clients during her years as a law professor at Harvard University.

He has criticized Warren for her legal work in the 1990s for LTV Steel as it fought mandated health care payments and her work as a legal consultant for Travelers Insurance in a U.S. Supreme Court case.

“Voters are learning that contrary to your claim to always stand with middle-class workers, you have instead chosen to stand with large corporations and against workers,” Brown wrote.

Warren, a consumer advocate, said Wednesday that since she went into public service in 2008, she's made financial disclosures and released her client contacts.

But she has declined to release details about other firms she performed legal work for earlier. Asked Monday on WTKK-FM if she could produce a list of those firms, she said, “I don't have it.”

Brown said Harvard Law School requires faculty members to report outside activities each year.

Warren also faulted Brown for refusing to release the names of lobbyists he's met with since winning the 2010 special election to fill the Senate seat left vacant by the death of longtime Democratic Sen. Edward Kennedy.

“I am surprised to hear Senator Brown raise an issue around disclosure when Senator Brown clearly has many things that he has not wanted to disclose on his own,” she said.

In the new video posted Wednesday, supporters' war cries are heard escalating as Brown criticizes Warren's claims of Native American heritage. Brown doesn't react in the brief clip, posted by the Democrat-leaning Blue Mass Group.

The group posted a video on Tuesday showing staff members for Brown and the state Republican Party shouting war whoops and performing tomahawk chops during a rally days earlier in Boston's Dorchester neighborhood.

Brown spokeswoman Alleigh Marre issued a statement Wednesday saying Brown “regrets that members of his staff did not live up to the high standards that the people of Massachusetts expect and deserve.”

Warren has said she was told growing up that her mother was part Cherokee and part Delaware Indian, but she hasn't offered any documentation of that heritage. She called both videos appalling, and American Indian groups also decried the actions shown.

The principal chief of the 310,000-member Cherokee Nation, Bill John Baker, a Democrat, called the behavior offensive and racist.

“It is those types of actions that perpetuate negative stereotypes and continue to minimize and degrade all native peoples,” Baker said in a statement.

The National Congress of American Indians, which describes itself as the nation's largest American Indian and Alaska Native advocacy group, called the videos disturbing and called on Brown to take “corrective action immediately.”

The group's executive director, Jacqueline Pata, also faulted Warren for allowing the public discourse about American Indian identity to become misrepresented and failing to educate the public about federal rules “that make proving Native ancestry very difficult for some people.”

She also criticized Warren for not meeting with Native American media groups.

Gov. Deval Patrick, a Democrat and Warren supporter, faulted Brown.

“If this is what they do in public, what do they do in private?” Patrick told reporters. “The tone is set at the top.”

Brown's campaign issued a comment from George Thomas, who identified himself as a Pequot and member of the Affiliated Tribes of New England and called Warren's heritage claims “insulting.”