More than 400 people turned out for a benefit concert last night at Catholic University to honor the memory of those who have died in the District's group homes for people with mental disabilities.

Attendees at the Hartke Theatre listened to performers after D.C. Mayor Anthony A. Williams (D) spoke about the importance of never forgetting the more than 100 people who have died.

"This is a fitting way to remember our brothers and sisters who have died," Williams said. "It shows the spirit and talent in our community, and it honors the memory of those in our community who have lost their lives."

Williams was joined by the university president, the Rev. David M. O'Connell. The Rev. Richard Birkel, president of the Lt. Joseph P. Kennedy Institute, told the audience that it's the responsibility of government agencies to protect those with mental and physical disabilities.

Williams said that "government has no more essential role than to protect the well-being and the rights of our most vulnerable citizens," adding that he was fully committed to seeing that the system that neglected those who died was overhauled.

"All of us recognize that this is more than a civic issue. It's a moral issue," he said.

Institute officials said the focus on group home deaths is in response to a series of articles in The Washington Post that found 350 documented cases of abuse and 116 unexamined deaths of group home residents in an industry marked by corporate fraud and government neglect.

The institute has a 50-year history of working with the mentally retarded and was chosen by Williams last week to lead a coalition that will temporarily take over case management duties while a new management team is established for the city's mental retardation agency.

Performing first last night was Tony Melendez, who led the audience in rousing songs, including "La Bamba." Melendez, an internationally acclaimed Catholic performing artist, plays the guitar with his feet because he was born without arms.

Also performing was renowned Irish tenor Mark Forrest, who has a child with disabilities and who lost another child. Forrest sang a rendition of "Danny Boy" for the audience, who responded with a standing ovation.

Kevin McFadden and Redeemed finished the evening with gospel music. Warren Burns, director of development and public relations for the Kennedy Institute, said he hoped to raise $4,000 from the event. Proceeds will benefit the institute's residential services program for people with disabilities.

To read complete Post coverage of group homes and to see documents gathered by The Post, go to www.washingtonpost.com/invisible.