NYPD still searching for clues a year after mysterious Central Park explosion cost teen his leg

— -- Authorities in New York City are still searching for clues a year after a mysterious Central Park explosion left a Virginia teen badly injured.

The victim, Fairfax resident Connor Golden, now 19, was climbing rocks July 3, 2016, with two friends near the entrance of the Central Park Zoo, authorities said at the time. When Golden jumped from the rocks, he landed on a bag of explosives, detonating the device.

A portion of Golden's left foot was badly mangled, leading to the amputation of his left leg below the kneecap.

The NYPD and U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) are still engaged in an "active and vigorous" investigation as they attempt to determine who left the homemade explosive device at the park, NYPD Chief of Detectives Robert Boyce said at a news conference at the park this afternoon.

Police believe the device was placed at the scene several days before the explosion, Boyce said.

Authorities are asking for the public's help in the investigation, appealing to those who visited Central Park in the days and weeks before the explosion to check to see whether any photos or videos they took could help move the case forward, Special Agent in Charge of the ATF New York Field Division Ashan Benedict said.

"At any given time, people climb the rocks to get a better view of Central Park," Benedict said. "It could have been just about any visitor to Central Park that day."

Investigators have not yet identified any suspects or determined a motive, Boyce said, adding that police do not believe it to be a terrorist act.

A $40,000 reward has been offered for information leading to the arrest of the person or people responsible, Benedict said.

The device was made of a compound familiar to police because the materials are easily accessible and the instructions on how to make it are available online, NYPD Deputy Commissioner John Miller said.

The explosive was left about "50 feet from the main road on one of the most crowded weekends in Central Park," Miller said.

Golden returned home to Virginia more than three weeks after the incident.