NEW YORK -- The mother for a mentally ill, homeless veteran who was found dead in a 101-degree New York City jail cell said Friday she was angry at city officials for not keeping her son safe and announced plans for a $25 million wrongful death lawsuit against the city.

"I know he was yelling for help and nobody ever came," Alma Murdough, 75, said at a news conference, surrounded by family. "He was hollering for help and nobody came."

Her son, Jerome Murdough, 56, was jailed at the Rikers Island complex on a misdemeanor trespassing charge and was unable to make bail. He was discovered unresponsive in his cell in the early hours of Feb. 15, and a preliminary investigation found his internal body temperature was 103 degrees and the cell was 101 degrees.

In court papers filed Friday in state Supreme Court in Manhattan, her attorney took a step toward suing the city, asking a judge to prohibit city officials from erasing any recordings regarding the death of his client's son and to preserve and obtain all evidence -- including 911 communications, photos, video and logbooks.

The lawyer, Derek Sells, has argued Murdough's death was caused by carelessness and negligence by Department of Correction employees.

Murdough's death was preventable, Sells said Friday.

"That's a very basic concept: Keep inmates safe," he said. "And that's what Rikers Island has failed to do, time and time again."

In a statement, mayoral spokeswoman Marti Adams said the administration would improve its efforts to make sure the DOC treated inmates appropriately.

"Mr. Murdough was a Marine veteran and his unfortunate death was a tragedy for this entire city," she said.

Prosecutors in the Bronx are investigating the death. Corrections officials have declined to comment, citing the ongoing criminal investigation.