Authorities on Friday offered a $25,000 reward for information leading to the arrest and conviction of the person responsible for planting the device.
The July 3 explosion rattled a city already on edge from attacks around the world and left the athletic Connor Golden with a prosthetic leg. With the reward, authorities hope to bring renewed attention to a case that, according to law enforcement officials, has gone cold.
It was warm on that Sunday morning -- the day before Independence Day -- when Golden, an 18-year-old from the University of Miami, and two of his friends, jumped off a rock in the park.
Golden landed on a pressure-sensitive shopping bag loaded with a deadly chemical mix. He suffered severe injuries and underwent surgeries to remove the lower part of his left leg.
Witnesses said the sound of the blast ripped through the park like a shot from a "cannon," scaring birds off trees. Some assumed it was a firework given the holiday weekend.
Explosive used in terror attacks
Investigators initially thought along those lines too -- evidence suggested the work of amateur hobbyists possibly experimenting with explosives during the July 4 festivities, bomb squad commanding officer Lt. Mark Torre said shortly after the blast.
Investigators said in July they believed someone was testing how to make the explosive
, which they say is common.
The device had been made with the homemade explosive triacetone triperoxide (TATP), which has been used in terrorist attacks -- including in the Paris attacks last fall and by the so-called "shoe bomber" Richard Reid.
But despite witness interviews and reviews of surveillance video and cell phone tower records, law enforcement had made no arrests as of Friday.
Golden and his two companions, who were both uninjured, are not believed to have played any role in the construction of the explosive device, authorities said.
The only major lead -- a scrap of the bag that led authorities to a defunct bakery in New Jersey -- did not pan out.
Reward offer not tied to new development
On Friday, the federal Bureau of Alcohol, Tobacco, Firearms and Explosives and the New York Police Department announced the reward to "spur some people to come forward with information who may not have done so before."
"Perhaps someone will remember some forgotten or unreported detail that may prove important to the investigation," said Matthew Myerson, a spokesman for the ATF New York field division.
The decision to offer the reward was not tied to a particular development in the investigation or elsewhere, Myerson said. In an interview, Connor's father, Kevin Golden, said his family was excited about the prospects of the reward.
"It's not good that they don't have a bunch of leads to work on, but they're doing something about it and hopefully that will generate more leads from the public," Golden said.
Connor Golden, now 19, was able to return only a week late to the University of Miami for his sophomore year, where he's making steady progress, his father said.
The rehabilitation process is slow, and practice with the prosthetic is like a whole new way of walking, he said, but the family is encouraged.
"He was just telling me today he thinks there will come a time in the not too distant future where he'll feel like windsurfing again," Golden said. "It's amazing to think of him doing that."