Joseph Leos, left, with the police

A 58-year-old man was in custody on Thursday in connection with the shooting to death four decades ago of his teenage friend in a small southwestern Pennsylvania town, prosecutors said.

Joseph Leos, of Mount Pleasant, Pennsylvania, faces one count of criminal homicide in the 1974 slaying of his 14-year-old friend, John Watson.

Local media quoted Fayette County District Attorney Jack Heneks as saying that the case represented a triumph of “old-fashioned police work” and “using updated techniques.”

An attorney for Leos could not immediately be identified.

Leos was arrested on Wednesday, about six years after an investigation into Watson’s death was reopened.

During the investigation, Pennsylvania State Police tested a coat Leos had worn the night of Watson’s death and found five distinctive particles of gunshot residue on it, Heneks said. The residue ultimately led to Leos’ arrest, he added.

Leos, who was also a teenager at the time of the shooting, lived near Watson in the Wheeler Bottom area of Dunbar Township, about 50 miles southeast of Pittsburgh.

Prosecutors say Leos is suspected of slaying Watson because of an “interpersonal relationship” between the two boys. They did not elaborate.

On the night of the shooting, Watson left home on his bicycle to buy cigarettes for his adult family members. Less than an hour later, Leos went to Watson’s home and told the boy’s family that “something terrible has happened to Johnny,” the complaint said. Leos was ignored initially but an hour later the family started a search, according to the complaint.

Watson’s body was found the following day next to Leos’ home.

An autopsy showed that Watson had died from a single .22 calibre gunshot wound to the back of his head.

Heneks said he did not know why the case remained unsolved for so long, but he noted that the technology used to test the coat for gunshot residue was not available in 1974.

The case had not been discussed much in the community in recent years, but was still of concern to Watson’s family, Heneks said.

Leos was arraigned on Wednesday but did not enter a plea. He is scheduled for a preliminary hearing on March 3.