They set up the drug deal via Snapchat, authorities said, and arranged to meet in the parking lot of a Phoenixville Dunkin' Donuts.

On the evening of Dec. 27, Jayson Ortiz-Cameron, 15, thought he was arriving there to buy marijuana. But Robert McCoy and Brian Corsey had other plans, officials say.

According to the Chester County District Attorney's Office, McCoy and Corsey intended to rob Ortiz-Cameron and his friend. Within minutes, the groups would engage in a back-and-forth, and Ortiz-Cameron would end up dead from a single gunshot wound to the head. 

Last week, McCoy, 22, of Pottstown, who arranged the drug deal, was charged with second-degree murder, robbery, conspiracy, and related offenses, officials said. Corsey, 24, of Philadelphia, the alleged shooter, remained at large Tuesday.

"The senseless murder of a 15-year-old boy was the result of a petty drug deal gone awry," Phoenixville Police Chief Tom Sjostrom said in a statement. "It is a tragedy that reinforces the dangers of all illegal drug use in our community."

The events of that December evening were captured on surveillance footage. Shortly after 7 p.m., McCoy, Corsey, and another man whom police did not identify arrived at the Dunkin' Donuts on the 200 block of Nutt Road. According to court documents released Tuesday, they circled the parking lot in an attempt to ensure they were not under surveillance. The three men, who were in a black Ford Focus, made contact with Ortiz-Cameron and his friend behind the Dunkin' Donuts.

Within minutes, police say, there was a confrontation. Ortiz-Cameron and Corsey ended up alone behind the parked Ford. Ortiz-Cameron's friend told police that when he tried to approach Ortiz-Cameron and Corsey, McCoy held him back, saying, "You don't want to go over there," according to the documents. Ortiz-Cameron's friend, whose identity police said they are withholding for his safety, then said he heard a shot and saw Ortiz-Cameron fall to the pavement.

The third man, who arrived with Corsey and McCoy, never got out of the car, according to police.

Ortiz-Cameron was pronounced dead at the scene. Corsey and McCoy fled. Over the course of the investigation, two witnesses helped police identify McCoy as the person who arranged the drug deal that evening, according to the documents.

Since his April 25 arraignment, McCoy has remained jailed without bail at Chester County Prison. No attorney for him was listed on court documents as of Tuesday.