The chief of the Peace Corps appeared on Capitol Hill on Wednesday to express regret for the agency’s failure to respond with compassion to a series of rapes of young volunteers and the recent slaying of another while they served overseas.

Director Aaron S. Williams told angry lawmakers on the House Committee on Foreign Affairs he was “amazed and shocked” when he learned of the crimes, which he said gave him “great anguish.”

He acknowledged that the Peace Corps has not been “sufficiently responsive or sensitive” to crime victims and their families while they are still volunteering and after they come home. He said that the agency has taken steps in the 20 months since he took the top job to improve training for volunteers and staff and that he is ready to work with Congress on long-sought legislation to change how victims are treated.

But as the respected government organization founded by President John F. Kennedy celebrates its 50th anniversary, it was the dramatic testimony of three rape victims and the mother of the slain volunteer that took center stage.

The women’s harrowing experiences in developing countries arose in different circumstances at different times. But the witnesses’ themes were the same: They said the Peace Corps did little to train its workers and volunteers in strategies to avoid or deal with violent attacks. And in the aftermath, they said, the message from top officials was clear: The victim was to blame.

“Apologies without action are useless,” said Carol Marie Clark of North Carolina, who accepted a posting in Nepal shortly after graduating from Wake Forest University in 1984, only to be told by her local program director that female volunteers would have to have sex with him to receive their living expenses. Three months later, he raped her and got her pregnant, she testified.

Lois Puzey said she lives a “heartbreak every day” from the loss of her daughter Kate, who was killed at 24 in a remote village in Benin in 2009. She was found with her throat slit shortly after she urged her country director to terminate the contract of a Peace Corps employee who she knew, according to her family and friends, had raped students at the school where she taught. Her mother said she believes the Peace Corps helped cause Kate’s death because an e-mail to her boss suggesting the man be fired fell into the hands of the accused killer’s brother and was not kept confidential.

Jessica Smochek joined the Peace Corps in 2004 as a volunteer in Bangladesh, where she was gang raped by local men after months of harassment, she testified. When she returned to Washington to debrief with Peace Corps staff about what happened to her, “Rather than feeling safe and supported, I felt belittled and blamed,” she said. The country director in Bangladesh told other volunteers about her rape and blamed Smochek for being out alone after 5 p.m., she said.

The former volunteers who are going public with their ordeals are attracting promises of legislation from Congress and what Williams called a new era of reform from Peace Corps’ top managers. He vowed to end what he called a culture of “blaming the victim.” He said an outdated training video that shows past sexual assault victims discussing what they did wrong to bring on the assaults will be replaced.

Williams suggested several other reforms, including staff counsel to victims about sexual violence and advocating for them before and after they leave the organization, better training for volunteers and staff, and anonymity for whistleblowers such as Puzey.

Lawmakers on the committee said they were moved by the women’s accounts — and outraged that for years, as reports of sexual assaults against Peace Corps volunteers have surfaced, little has changed.

“For the last 11 years, I’ve heard what we ought to do, and we haven’t had one single piece of legislation,” said Rep. Donald M. Payne (D-N.J.).

The Peace Corps now has more than 8,600 volunteers and trainees serving in 77 countries. They range in age from their 20s to their 80s. From 2000 to 2009, more than 1,000 volunteers reported sexual assaults, including 221 rapes or attempted rapes, according to agency statistics. Because sexual crimes often go unreported, the incidence is likely to be higher than those figures, advocates say.

A 2010 report by the agency’s inspector general found that when compared with crime statistics gathered by the United Nations from 86 countries, Peace Corps volunteers suffered higher rates of rape and burglary than other nations reporting.