He is accused of injecting a 37-year-old man with methamphetamine, according to court documents in the latest charge.
The man survived the overdose but two gay black men have died in similar circumstances in Mr Buck’s apartment.
Gemmel Moore, 26, died of a methamphetamine overdose in the building in July 2017 and Timothy Dean, 55, died in the same way in January 2019.
Prosecutors declined to file charges in 2017 over Moore’s death, citing a lack of evidence.
Officials now argue, in court filings, that Buck targets vulnerable men and invite them to his home, according to Buzzfeed.
They believe Mr Buck has a fetish involving ”supplying and personally administering dangerously large doses of narcotics to his victims.”
“Buck is clearly a predator with no regard for human life,” prosecutors said, according to NBC News.
“His behaviour is malicious and beyond reckless.
“His fetish led to the grooming and eventual death of Gemmel Moore. Undeterred, defendant Buck then engaged in the exact same behaviour with Timothy Dean, leading to his untimely death. Shockingly, defendant Buck continued his path of destruction, nearly causing another fatal incident.
“His deadly behaviour has not stopped.”
Mr Buck faces charges of administering methamphetamine and maintaining a drug house. He is not facing any criminal proceedings in relation to Moore and Dean’s deaths.
He remains subject to a wrongful death civil lawsuit, filed in February by Moore’s mother.
That lawsuit alleges wrongful death, sexual battery, hate violence, drug dealer liability, negligence, infliction of emotional distress, and two violations of civil rights on the part of the 65-year-old.
An updated filing includes an accusation of human trafficking, alleging that Mr Buck paid Moore to travel from Texas to West Hollywood.
Los Angeles prosecutors say Mr Buck attempted to stop the third man, who has not been named, from seeking help after he overdosed on 11 September.
The 37-year-old eventually escaped the flat and reached a petrol station, where he called the police.
Officers later searched the West Hollywood home and discovered hundreds of photographs of men in compromising positions.
“I remain deeply concerned for the safety of people whose life circumstances may make them more vulnerable to criminal predators,” said Jackie Lacey, the Los Angeles district attorney.
“With this new evidence, I authorised the filing of criminal charges against Ed Buck.”
Prosecutors have asked Mr Buck’s bail be set at $4m (£3.2m), arguing that without a high threshold, another death was possible.
If convicted as charged, the 65-year-old faces a possible maximum sentence of five years and eight months in prison.
Mr Buck has previously denied all allegations of wrongdoing.
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