LOS ANGELES—Months after Los Angeles prosecutors declined to charge political donor and activist Ed Buck with the fatal overdose of a man in his home during sex, the feds stepped in and did it.

The U.S. attorney’s office accused Buck, 65, of injecting Gemmel Moore, 26, with a deadly shot of methamphetamine at Buck’s West Hollywood apartment in July 2017.

Two other men have overdosed at the house, according to authorities: Timothy Dean, 55, who died there in January, and an unidentified man who who survived his encounter with Buck earlier this month and called police.

A criminal complaint filed Thursday detailed accusations from other men that formed a portrait of depravity: a wealthy, white, politically connected hedonist who allegedly paid, cajoled or physically forced vulnerable sexual partners to do meth.

One man said he fell asleep in Buck’s home and woke up to find his arm red and sore from what he suspects was an injection. Another said Buck was known in the neighborhood as “Dr. Kevorkian” because of his reputation for providing drugs. Others suggested that Buck gave them beverages that appeared to have been spiked.

The men reported that Buck made them wear underwear that he kept sorted by color in bins and would photograph or video them. Chillingly, one man said Buck played for him videos of Moore “who appeared... to be scared,” the complaint said.

Some of the men said they emerged from stupors in pain. One reported he was bleeding from his anus, and metal clips were attached to his nipples.

Buck, a retired entrepreneur who has donated hundreds of thousands of dollars to Democratic politicians and liberal causes, was charged with one count of distribution of a drug causing death—which carries a minimum sentence of 20 years in prison.

He appeared briefly in court and will return for a bail hearing Sept. 26. U.S. Attorney Nick Hanna said prosecutors would ask a federal judge to keep Buck jailed until trial because he presents “a serious risk to public safety.”

Buck’s attorney could not be reached for immediate comment on Thursday but has previously denied that his client played a role in the men’s deaths.

The federal prosecution was announced one day after Los Angeles County District Attorney Jackie Lacey hit Buck with three less serious state charges in connection with the man who overdosed on Sept. 11—who told investigators that Buck injected him with meth nearly every day for a month.

L.A. officials have been dogged by criticism from Moore’s and Dean’s families and community activists that they were not aggressive enough in investigating Buck.

At their joint press conference with the feds, Lacey and L.A. County Sheriff Alex Villanueva sounded defensive as they answered questions about why it took so long to bring charges against Buck.

Lacey insisted that L.A. investigators followed every lead given to them by activists but said they were never able to gather enough admissible evidence to charge him with the two deaths under state law.

“We interviewed every person that was brought before us. They didn’t talk to us. They lawyered up. We made an effort to talk to every person who witnessed something,” she said.

She could not explain why the victims spoke to the feds about their harrowing experiences.

Lacey, who returned a $100 donation from Buck after he was implicated in the overdoses, said her office was only able to make an arrest after the last victim fled and called 911.

“The surviving witness’ statements gave us the break we needed,” Lacey said. “We needed someone live, willing to come to court and be cross-examined.”

The federal complaint says that victim met Buck on Adam4Adam in June, was picked up in a car from Skid Row, and was brought to his West Hollywood apartment. After he moved in July 29, Buck injected him with meth nearly every day, until Sept. 11, when he gave him a double dose that caused overdose symptoms.

The victim asked for a Klonopin pill, but Buck refused to give him one, the complaint says. He also would not call an ambulance, so the man eventually left and asked a passer-by and a gas station employee to call 911, the court documents say.

The state charges lodged in connection with that incident—battery causing serious injury, administering methamphetamine, and maintaining a drug house—carried up to four years in prison.

The feds, Lacey said, had “more options” and stiffer penalties at their disposal. The federal charge of distribution resulting in death—which could result in a life sentence—doesn’t have a state counterpart, Hanna said.

—Tarpley Hitt reported from Los Angeles and Tracy Connor reported from New York