STATEN ISLAND, N.Y. -- Three young men Mariners Harbor men were arrested Friday on murder charges in Tuesday's slaying of a Chinese food deliveryman in their community, said police.

Cops identified the suspects as James Sanders, 16, of South Avenue; Otoniel Carty, 17, of Bush Avenue, and Devin Hill, 19, of the 100 block of Andros Avenue.

Sanders is believed to have gunned down Richard Salvia, 50, outside 244 Grandview Avenue, said a source with knowledge of the investigation.

Carty served as lookout and Hill was an accomplice, said the source.

All three live within blocks of where the killing occurred.

Police recovered what they believe to be the murder weapon, a .38-caliber derringer, said the source. The weapon was found at the house of a female friend of Carty's, where he tried to ditch it, another source said.

Under questioning, one of the suspects said they had planned the robbery for a week, the source said.

One of them also had the cell phone used to call Crown Palace restaurant in Port Richmond for the delivery, said the source.

Police sources told the Advance the presumed robbery was caught on video cameras in the area.

The suspects are expected to be arraigned Saturday in Stapleton Criminal Court.

All three are charged with second-degree murder, three counts of attempted first-degree robbery and two counts of attempted second-degree robbery, said police.

Sanders and Carty are also charged with criminal weapon possession, said cops.

Online state court records show Sanders was arrested on Dec. 5 and charged with disorderly conduct in a unrelated case. Incident details were not immediately available; however, the case is pending and Sanders is slated to appear in Stapleton Criminal Court on April 17.

According to Advance reports, an Ontoniel Carty was arrested on Oct. 10 and accused of punching a male teacher in the face and spitting on him inside South Richmond High School.

South Richmond caters to students with developmental and behavioral problems.

He was charged with felony and misdemeanor assault, as well as harassment, according to information then from District Attorney Daniel Donovan's office.

That case's disposition was not immediately available Friday.

Authorities said Salvia was ambushed as he delivered a food order to a fenced-off house sandwiched between two abandoned houses on a dead end street, at 8:45 p.m.

He was shot in the back of the head, said police. The suspects fled.

What's curious is that Salvia still had $136 in cash on his person. He didn't have a wallet when he was found, sources said -- and it's not clear if he wasn't carrying one or if it had been stolen.

The shooting has rattled delivery workers in the borough.

-- Staff writer John Annese contributed to this report.