Williams, an Emmy-nominated actor, was known for his role as Omar Little on the HBO show, "The Wire." He also played a menacing mobster on the series "Boardwalk Empire."
Tragically, the 54-year-old died in September.
Prosecutors say Williams was sold heroin laced with fentanyl, CBS2's Kevin Rincon reported.
Nearly five months later, four people have now been arrested in connection to his death, charged with narcotics conspiracy. Three of those defendants made a court appearance in the city. The fourth was taken into custody in Puerto Rico.
According to court documents, on Sept. 5, 2021, Williams was sold the drugs by Irving Cartagena. Prosecutors released images which they say show the 39-year-old suspect hand-delivering the heroin, a day before Williams was found dead in his Brooklyn penthouse.
Luiz Cruis, Hector Robles, and Carlos Macci are also facing charges.
"This is a public health crisis and it has got to stop," U.S. Attorney Damian Williams said.
He said the four men knew of the actor's death, and continued selling fentanyl-laced heroin in broad daylight outside of residential apartments throughout Brooklyn and Manhattan.
"We will bring every tool to bear and we will continue to hold accountable the dealers who push this poison, exploit addiction, and cause senseless death," Damian Williams said.
Years before his death, Michael K. Williams had been open about his battle with drug addiction, calling it an everyday struggle.
CBS2's Kevin Rincon contributed to this report.
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