Two men from Dorchester were among four indicted last week on federal charges of running a heroin ring out of a Hyde Park three decker.

According to a court filing, Osvaldo Ortiz-Ventara, 23, and Weslley Hernandez, 25, served as couriers for the ring. They allegedly delivered the fatal dose of heroin laced with fentanyl and an animal painkiller to an intermediary who sold it to a Braintree man whose girlfriend found him dead of an overdose in January.

Ortiz-Ventara is now in federal custody on charges of conspiracy to distribute heroin and distribution of heroin. Hernandez, charged with the same offenses, is on the run, the FBI and the US Attorney's office in Boston report.

Also indicted: The alleged ringleader, known to authorities as Cesar Gonzalez, and Kevin Sanderson, 28, of Quincy, to whom Ortiz-Ventara and Hernandez allegedly delivered heroin at his job at a Braintree car dealership, including the dose that killed Steven Radeos.

Radeos's cell phone allegedly led authorities to Sanderson, who in turn agreed to collect evidence against Gonzalez - in part by making more than 20 additional purchases from him after Radeos's death.

Court documents say that Gonzalez's brother continued the operation from an apartment at 1455 River St. in Hyde Park even after his brother was arrested.

According to an affidavit filed by a Braintree detective who investigated the ring, Gonzalez knew his drugs were more potent than usual; he even color coded his wares based on how strong they were.

Sanderson, in turn, allegedly warned Radeos via a text message to be careful with the $100 worth of the heroin he was about to deliver because it could mess him up.

Shortly before 6 a.m. on Jan. 24, Radeos's girlfriend called 911 to report her boyfriend's apparent overdose, the affidavit states. EMTs took him to Quincy Medical Center, where he died the next day.