Two men charged this week with double murder in connection with a shooting at San Francisco’s Crocker Amazon Playground were working with a city-run violence-prevention program that was launched in 2012 in a bid to reduce homicides, a family member said Thursday.

Davante Robinson and Gregory Morton III were charged in the deaths of Kenyatta Butler Jr., 18, of San Leandro and Donzel Gaines, 19, of San Francisco. The victims were found dead in a 2002 Camaro in the parking lot of the park around 9:15 a.m. on March 9.

Authorities have not commented on a possible motive in the case, but prosecutors alleged that Robinson and Morton acted on behalf of a street gang.

Crystal Robinson, Davante Robinson’s mother, said Thursday that she was “nearly positive” that her son and Morton had been working on the morning of the shooting with a city violence-prevention and job-training program called Interrupt, Predict and Organize.

Robinson and Morton had been working with the San Francisco Recreation and Park Department doing general maintenance work — cleaning parks, doing light repairs and replacing worn-out equipment — for about six months before they were arrested, said Crystal Robinson.

“I know he needed the work, but he enjoyed what he did,” she said.

Participants in the program are supposed to be supervised while working, and all absences are to be noted on time sheets, according to a supervisors handbook provided to The Chronicle. Citing the ongoing investigation, parks department officials declined Thursday to give information about the two men — including whether they had worked with the department.

Interrput, Predict and Organize was started by Mayor Ed Lee, Supervisor Malia Cohen and the Police Department. It is designed to place at-risk individuals with various city departments to give them job experience, with a goal of full-time employment after a year-long internship, said Trent Rhorer, executive director of the Human Services Agency, which oversees funding for the program.

“We feel that, so far, it has been a successful diversion in keeping people off the streets,” he said. “We’re basically trying to give folks an alternative to making money on the streets in illicit ways.”

Since the program began, roughly 90 people have entered job training, Rhorer said, with about 60 percent completing the training. Of those who completed training, he said, about 75 percent were placed in full-time jobs. He said the program costs roughly $450,000 a year.

Cohen said that because the city doesn’t have a clear definition of violence prevention, it can be hard to gauge such programs.

“I’m hesitant to say the program is a failure, but we need better metrics to judge it by,” she said. “If infrastructure changes need to be made within the program, that is where my focus lies.”

Attorneys for Robinson and Morton did not return calls seeking comment Thursday. The two men have not entered a plea, and are scheduled to return to court Monday. Both are in custody in lieu of $5 million bail.

Kale Williams is a San Francisco Chronicle staff writer. E-mail: kwilliams@sfchronicle.com Twitter: @sfkale