Courtesy Pocono Mountain Regional Police William McRae, charged with murdering his accomplice in a Craigslist-related robbery.

A Pennsylvania man was charged Wednesday with executing his accomplice in a Craigslist-related robbery because he had loose lips, police said.

William McRae, 23, was tracked down to New York City four months after Brandon Fraser, 20, was found shot to death in a car in the Poconos.

Court documents allege the two men hatched a plan over the summer to use the "casual encounters" section of the online classified site Craigslist to find a robbery victim.

They enlisted a friend, Emily Woodman, to lure the man to Pine Tree Beach and entice him down a dark path, where they beat him with a baseball bat, pistol-whipped him and tied him up, a police affidavit said.

The duo allegedly robbed $100 in cash, his cellphone and credit cards. They also forced him to divulge his credit card PIN number and the names of his children with a warning not to report the robbery to police, according to the affidavit.

Within a week, detectives had identified Fraser as a possible suspect through the number on the Craigslist ad and video of him trying to use the stolen ATM card.

But Fraser was never arrested because a day later, he was found shot in the head in the back seat of his Nissan Altima in a lake-side community parking lot.

Investigators soon learned that Fraser was friends with McRae, who told them he was with Woodman driving to Scranton at the time of the murder, the court papers said.

The alibi soon came apart, and in late November, Woodman confessed, telling detectives that after the robbery, McRae "started to become upset with Fraser because he was being careless with covering up the crime," the affidavit said.

"She related that McRae advised her that Fraser was telling people about the robbery and that he 'needed to go," it said.

Woodman, who is being held on a robbery charge, told police she drove McRae to a house where he picked up a shotgun and dressed in a hunting suit and ski mask, police said. He hid in the woods near the parking lot, texted Fraser to meet him and then shot him through the rear window, court papers said.

The affidavit outlined other evidence, including a sweatshirt found at Woodson's house that was matched to Fraser's DNA this week, and an analysis of cellphone signals that poked a hole in his alibi.

McRae is charged with robbery and criminal homicide.

Pocono Mountain Regional Police Chief Harry Lewis praised "outstanding work by our detectives" and thanked the Pennsylvania Attorney General's office and the U.S. Marshals and NYPD for helping to nab McRae in New York.