A nearly half-century wait for justice is over.

The man who shot and killed 18-year-old Theresa Marcoux and 20-year-old Mark Harnish in West Springfield in 1978 has been arrested thanks to a tip that led to new revelations in the cold case, Hampden District Attorney Anthony Gulluni announced on Wednesday.

After decades of working to find the killer, investigators arrested Timothy Joley, 71, at his residence in Clearwater, Fla., on Oct. 30, charging the man with the murders of Marcoux and Harnish.

Authorities obtained a two-count murder complaint and arrest warrant for Joley out of Springfield District Court the day before he was taken into custody in Florida. A circuit judge in Pinellas County waived extradition last Tuesday, and Joley will return to the Bay State “in the coming weeks to face these charges,” Gulluni’s office said in a release.

Joley is being held without bond.

“I admire and respect you for your patience, resolve and the faith that I know you have maintained over these many years,” Gulluni told family members of Marcoux and Harnish on Wednesday. “Sadly, the parents of Theresa and Mark are deceased and never knew either answers or justice for the brutality that was inflicted upon their children.”

“Throughout the years, however, this office has maintained contact with the extended families of both victims,” he added. “Their desire for justice, and ours, has never extinguished.”

Investigators quickly concluded that Marcoux and Harnish had been shot while in the passenger compartment of a pickup truck the morning of Nov. 19, 1978, with their bodies being moved to a roadway rest area where their remains were later found.

“The forthcoming investigation saw painstaking efforts to document and photograph the scene, with physical and biological evidence collected by investigators,” Gulluni’s office wrote in a release. “The rest area was thoroughly searched for evidence, yet no firearm was recovered.”

Investigators located a “latent print in what appeared to be blood on the passenger-side vent window” inside the truck, but they eliminated Marcoux and Harnish as a possible source.

The print was entered into the state’s automated fingerprint ID system, and investigators over the decades compared it to roughly 70,000 “known fingerprint cards,” the DA said. The attempts to make an identification proved futile.

That changed when the DA’s office received information last month from an individual who provided Joley’s identification and his purported involvement in the murders.

The DA’s office said it enlisted a pair of law enforcement investigators “with extensive experience in fingerprint analysis, comparison, evaluation and verification.” They each determined that the unknown latent print recovered from Harnish’s truck “originated from Joley’s left thumb.”

The investigators also learned Joly had been a licensed gun owner in November 1978 who purchased a Colt handgun about a month before he shot and killed Marcoux and Harnish, Gulluni said.

“A guiding principle of the Hampden District Attorney’s Office is to relentlessly pursue justice for the citizens of Hampden County, particularly for those who are impacted by crime” his office wrote in its release. “This pursuit of justice is never easy, and it sometimes takes a long and circuitous route.”