Two Dorchester teenagers, one 16 and the other 17, were held without bail today as they faced murder and robbery charges stemming from the fatal shooting of 71-year-old Geraldo Serrano in an Upham’s Corner convenience store Sunday morning, Suffolk County District Attorney Daniel F. Conley said.

Acting on Suffolk prosecutors’ requests, Roxbury District Court Judge Robert J. McKenna withheld bail and ordered MARTIN FREELES (D.O.B. 1/21/93) and ONYX WHITE (D.O.B. 10/6/93) to return to court on April 23. Both youths are charged with murder, armed robbery while masked, and firearms offenses.

“What a terrible, terrible tragedy this case is,” Conley said. “A beloved family man is lost to violence, and two very young men now face life in prison. The arrests give us some satisfaction, but we’re keenly aware of the void left in so many lives today.”

Assistant District Attorney David Fredette told the court that a round-the-clock investigation by Boston Police homicide detectives and Suffolk homicide prosecutors had developed evidence that Freeles and White entered the Hermanos Unidos market on Dudley Street shortly after 10:30 a.m.

Their faces were covered and at least one of the assailants brandished a handgun, Fredette said. As the clerk behind the counter complied with a demand for cash, Fredette said, Serrano made his way from the back of the store to the front. He resisted the robbery, the prosecutor told the court.

One shot was fired, Fredette said, and Serrano grabbed his cane. When he did so, a second shot was fired and struck Serrano. That shot mortally wounded the Roxbury family man, who died a short time later. The assailants fled with a quantity of cash.

In the days that followed, Boston Police homicide detectives and Suffolk prosecutors received some information from the public and developed additional information in interviews and grand jury proceedings.

A firearm believed to be the murder weapon has been recovered, Fredette said, and the two defendants have been positively identified as the assailants who entered the store, robbed its clerk, and shot Serrano. The investigation still remains very active, prosecutors say.

Freeles is represented by attorney Steven Sack. White is represented by attorney Michael Bourbeau. At 16 and legally a juvenile, he will be charged and tried as an adult under Massachusetts law.

Catherine Yuan is the victim-witness advocate assigned to the case by Conley’s office.