An innocent bystander also narrowly escaped injury when a stray bullet from the shooting came through her front window, barely missed her head and lodged in her wall, Chitwood said.

At about 10:50 p.m., as Tyrone Nelson, 22, and Jimmy Armstrong, 26, were leaving Nelson's girlfriend's house on Hampden Road near Marshall in Upper Darby, they were approached by two or three men who told them to "give it up," according to police.

Nelson, who was wearing a gold and diamond necklace valued at thousands of dollars, was shot in the head as he tried to take the necklace off, Chitwood said.

Armstrong subsequently ran from the scene but only got about 15 yards away before he was shot four times in the head, police said. Last night, he remained on life support in "very critical condition" at the Hospital of the University of Pennsylvania. He is not expected to live, according to Chitwood.

Nelson, who lists two addresses - his girlfriend's and one at North 62nd Street near Haverford Avenue in Philadelphia - was pronounced dead at the scene.

The gold and diamond necklace was left at the scene and the assailants, who remain on the lam, fled on foot, Chitwood said.

According to police, both victims have significant criminal records in Philadelphia and authorities believe the killings may be drug related.

"The robbery was the ruse but the assassination was the goal," Chitwood said. "These guys were lying in wait. They knew exactly what they were doing and we believe the victims were specifically targeted."

A pizza deliveryman about three blocks away from the scene saw a man walking at a fast pace throw a gun into a sewer outlet shortly after the shooting, Chitwood said. Police retrieved the gun, which they believe may be one of the weapons used in the shootings.

Officers continue to check rooftops and sewer outlets in search of more weapons and other evidence, Chitwood said.

He stressed that gun violence is increasing in Upper Darby, noting that while police were responding to the shooting last night, they got another call for a burglary in which two firearms were stolen.

Nelson's death is the second homicide in the borough and the 12th homicide in Delaware County this year. *