Lt. Larry Leeson, a Baltimore police spokesman, said DelGiorno had moved into an apartment in the same block as the bar, Eddie's Lounge, just hours before the altercation. A Philadelphia source said DelGiorno moved in some days earlier.
Leeson said DelGiorno and Forline apparently did not know Hemerlein.
DelGiorno's father, Thomas "Tommy Del" DelGiorno, is scheduled to take the witness stand here Monday to testify against reputed mob boss Nicodemo ''Little Nicky" Scarfo and eight associates charged with the September 1984 killing of mob figure Salvatore Testa.
Prosecutor Barbara Christie would not comment on the arrest. On Wednesday, she asked Common Pleas Judge Albert F. Sabo to recess the trial for two days, saying her next witness - the elder DelGiorno - would not be available until Monday.
The incident caused DelGiorno's testimony to be postponed, said someone close to the trial.
An investigative source confirmed that Forline is the nephew of the late Frank "J.R." Forlini, a Delaware County concrete company executive and reputed collector for loan sharks. Forlini, who also spelled his name Forline, was found shot to death in Marple Township in February 1985, in an apparent organized crime contract killing. That killing remains unsolved.
The elder DelGiorno, a former mob capo, and his family have been in federal protective custody since he turned informant in November 1986. He is testifying in a series of trials against his former associates, and hopes to receive a new identity through the Witness Protection Program when he is done.
According to Leeson, Robert DelGiorno and Forline began arguing with Hemerlein around midnight. They took their dispute outside, where Hemerlein began besting DelGiorno in a fistfight.
Leeson said Forline went to DelGiorno's apartment, returned with a .357 Magnum, and shot Hemerlein once in the face. After dragging the body to an
alley, the two left the scene in a car bearing Pennsylvania tags.
Leeson said the two turned themselves in to a Pinkerton security guard at a Bethlehem Steel Plant in Baltimore County at about 2 a.m.
"They said they had just killed a man in Baltimore, and dropped the gun in front of him," Leeson said.
Leeson said the two were charged with first-degree murder, and may be indicted by a grand jury next week.
Wayne G. Davis, special agent in charge of the Philadelphia FBI office, declined to comment on the arrest.
Although his whereabouts were supposed to be kept quiet, young DelGiorno made frequent visits to South Philadelphia, and his friends frequently visited him, a source said.