On a long holiday weekend in New York City, Central Park is a must-stroll destination for many tourists and locals alike.

Police say that's just what a group of friends from the Washington, D.C., area were doing Sunday morning when one of them stepped on explosive material.

The Associated Press reports: "The homemade gadget was like an 'explosive experiment' that was probably designed to 'make a large noise, maybe make a flash,' concocted by someone with a basic understanding of chemistry, said Lt. Mark Torre, commanding officer of the New York Police Department's bomb squad."

Authorities say Connor Golden, who was visiting from Fairfax, Va., suffered a severe leg injury.

One of Golden's friends, Thomas Hinds, tells WABC-TV, "We were climbing down the rocks, Connor was 6 feet behind me and all of sudden I felt the explosion on my back. The explosion sounded like a gunshot next to my ears."

The New York Times reports:

"After the explosion, (Golden) was lying against a boulder with his left leg below the calf severely wounded. Someone had tied a strip of blue fabric around his leg as a tourniquet before emergency workers carried him from the park on a stretcher. The authorities said Mr. Golden was taken to Bellevue Hospital Center in Manhattan, where he was in serious but stable condition. He was undergoing surgery, officials said on Sunday evening. They added that they believe Mr. Golden, who was with two friends at the time, had stumbled upon the material."

Investigators do not believe that the injured man and his friends were responsible for creating the material, which had been left in the park for at least a day.

The blast happened at 11 a.m. in the southeastern end of the park. At first people who had heard the explosion blocks away thought it had something to do with July 4 celebrations.

Authorities found no evidence that the explosion was related to terrorism but The New York Times reports President Obama was briefed about the incident.

The FBI, along with the NYPD, are looking into the incident which they believe was a fireworks experiment.

"It is not unusual for the public to make or try to create homemade fireworks around the Fourth of July," John O'Connell, a deputy police chief for counterterrorism with the NYPD, told the Times.

Mayor Bill de Blasio sent a tweet cautioning people to enjoy fireworks safely: "Fireworks are fun — but let's leave them to the professionals."

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