The top U.S. Marine vowed in a Senate hearing to hold members of the Marine Corps accountable for sharing nude photos of female Marines online. But many members of the Senate Armed Services Committee responded with tough questions Tuesday, asking why more isn't being done to protect female service members.

"We have to commit to get rid of this perversion to our culture. Enough is enough," Marine Corps Commandant Gen. Robert Neller told the senators. "We will take action to correct this stain on our Marine Corps."

The scandal has prompted a Pentagon investigation, and Neller said perpetrators may be subject to punishment through the Uniform Code of Military Justice.

Neller added that officials are in the process of revising their policy to make the consequences of actions like the photo-posting more direct, and said he believes that the current policy is not taught to Marines "with enough time or reinforcement."

The explicit photos at the center of this scandal were published on a private Facebook group with some 30,000 members called Marines United, initially set up for current and veteran Marines to support each other. Neller said the photos were shared on a smaller group linked to on the main page.

"Some of the photos included detailed information," NPR's Tom Bowman reported, "and some of the women have been subject to harassment." The Facebook group has been taken down, but the photos remain online on a different page.

"It's hard to believe that something is really going to be done when we hear this repeated again and again, and we see these kind of situations again and again," said Sen. Jeanne Shaheen, D-N.H. "Why should we believe that it's going to be different this time than it's been in the past?"

Similarly, Sen. Kirsten Gillibrand, D-N.Y., said that after reports of online exploitation of women dating back to 2013, promises to fix the problem "ring hollow." She said: "You have demanded that you maintain control of all these issues, but where is the accountability for failure? ... I am very concerned that this is part of a culture that is resulting in the high levels of sexual assault."

Gillibrand has been an "outspoken critic of the way the Pentagon has handled sexual harassment and assault," Tom added. And Neller was frank in his response to Gillibrand, taking responsibility for the current problem:

"I don't have a good answer for you. I'm not going to sit here and duck around this thing, I'm not. I'm responsible. I'm the Commandant. I own this. ... I know you've heard it before, but we are going to have to change how we see ourselves and how we treat each other. That's a lame answer, but ma'am, that's the best I can tell you right now. We've got to change, and that's on me."

Tom added that the Marine Corps has prided itself on being "macho and traditional." He described the somewhat uneasy transition for women into ground combat roles:

"There are some who are having trouble accepting women who recently started going into ground combat jobs. Now two years ago ... to get ready for women in ground combat, all the Marines had mandatory training on 'unconscious prejudice' to help deal with any cultural resistance. [Neller] told senators today that he doesn't know if there's a connection between not accepting women and posting nude photos. What he did say was this: 'We have to change the way we see each other as Marines.'"

It's not just the Marines — Tom added that officials are also investigating similar websites linked to other services.

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