(CNN) Democratic donor Ed Buck now faces a federal charge of giving methamphetamine to a 26-year-old man who died of an overdose, a federal prosecutor said Thursday.

Buck, 65, is charged with one count of distribution of methamphetamine resulting in death, a criminal complaint said. He gave Gemmel Moore the dose of methamphetamine that led to Moore's death in Buck's West Hollywood apartment on July 27, 2017, according to court papers.

A second man -- previously identified by authorities as 55-year-old Timothy Dean -- died from a drug overdose in Buck's apartment in January , and Buck also gave drugs to several other men, one of whom suffered two overdoses several weeks ago, court papers said.

The prominent donor solicited men for sex in exchange for drugs and money, US Attorney Nick Hanna said. Buck is believed to have held victims against their will, and injected them with drugs against will, Hanna said.

Buck's attorney Seymour Amster declined to comment after the federal charge was announced.

Buck is expected to be arraigned in federal court on Thursday. Prosecutors will ask for Buck to be held without bond pending a trial because they believe Buck "poses a significant risk to public safety," Hanna said.

If convicted, Buck faces up to life in prison.

At the time of his death, Moore was living in Texas. Text messages between Moore and Buck "suggested that Buck purchased Moore's airline ticket," an affidavit said.

American Airlines boarding passes showed Moore left Houston on the day of his death and landed in Los Angeles around nine hours before his death, court records said.

Hanna said Buck brought Moore to Los Angeles "for the purpose of engaging in sexual activity. And then Mr. Buck agreed to pay the victim with money and narcotics."

On the day of Moore's death, Los Angeles Sheriff's deputies responded to Buck's 911 call that someone had stopped breathing in his home. Moore was found wearing only white socks on his feet and unresponsive on a mattress in the living room, court papers said.

Buck told sheriff's deputies Moore had injected methamphetamine and smoked marijuana two to three hours earlier in the restroom. But Buck said he did not see Moore injecting methamphetamine and did not know where Moore discarded the syringe, a statement of probable cause said.

Deputies saw drug paraphernalia including 24 syringes and five glass pipes in Buck's home, court papers said.

Moore's death was ruled an accidental methamphetamine overdose, according to the Los Angeles County Department of Medical Examiner-Coroner.

Moore's mother told investigators that her son reported that months before his death that Buck had "held Mr. Moore against his will and shot him up with drugs," Hanna said.

In February, Moore's mother filed a wrongful death lawsuit against Buck alleging that he injected her son with a lethal dose of crystal methamphetamine.

"We categorically deny all allegations of wrongdoing and look forward to litigating this matter in a court of law," Amster told NBC News then.

Additional alleged victims

Investigators have found 10 more victims, nine of whom said Buck "administered drugs to them or strongly encouraged them to ingest narcotics as part of agreements to be compensated for sexual services," Hanna said.

According to court papers, one unnamed victim said he fell asleep on Buck's couch on July 3, 2017, "and when he woke up his arm was tied to the couch, and was red and sore." The man said he believed Buck injected him with drugs while he was sleeping, court papers said.

Another unnamed victim, who was homeless, told authorities Buck was nicknamed "Doctor Kevorkian," and was "well known for compensating male prostitutes with drugs and money," the court papers said.

That victim said in their first meeting in Buck's home, Buck gave him $60 and methamphetamine in exchange for sex, and it was "part of Buck's role-playing and fantasy to inject people with methamphetamine."

Buck continued to solicit men for sex and distribute methamphetamine after two deaths in his apartment, court papers said.

Recent state charges

Buck already faces state felony charges of maintaining a drug house, battery causing serious injury and administering methamphetamine. His arraignment for those charges was postponed until October 11.

Buck is accused of injecting a 37-year-old man with methamphetamine at his West Hollywood apartment on September 11, the Los Angeles County District Attorney's Office said. The man suffered a nonfatal overdose.

"This is a case that there have been a lot of activists' interaction on it, thinking that charges should have been brought before there were," Amster said before the federal charge was announced.

"We will fight this case vigorously, but I'm not so sure legitimately there was ever enough evidence to ever cause this case to be filed until recently," he added.

Buck was being held on $4 million bail on the state charges.

Buck has donated to a number of Democratic candidates and PACs in recent years, according to information from OpenSecrets, a nonpartisan group that tracks money in US politics. Recipients rushed to return Buck's money after Dean's death.