Tumolo was last seen leaving his Philadelphia, Pennsylvania home to ride his bicycle to the house of his best friend, Jack Marino, on October 15, 1966. He never arrived and has never been heard from again. Tumolo's parents assumed he was with Marino and did not realize he was missing until the next morning, when he did not deliver newspapers for his paper route as scheduled. Authorities initially believed him to be a runaway. Prior to his disappearance, he had argued with parents; he was making poor grades and they wanted him to quit his paper route and focus on school. Five days after Tumolo went missing, two of his classmates claimed to have seen him. The police stopped looking for him after that, believing he was safe and did not want to be found.

Marino never believed Tumolo left of his own accord. The two teenagers were very close and Tumolo had never mentioned wanting to leave home. In addition, Tumolo was very close to his family, which included eight siblings, and it would be uncharacteristic of him to leave without warning. He also left behind an uncashed paycheck, some cash and other belongings in his bedroom, which would make little sense if he was planning on leaving forever. Marino is now a police officer and, decades after his friend vanished, he located one of the boys who claimed to have seen him in the days following his disappearance. The witness admitted he had lied about seeing Tumolo in order to avoid being punished for being tardy to school.

Marino theorizes Tumolo was struck by a vehicle while riding his bicycle, and the driver panicked and hid his body and the bike, which was also never found. Interstate 95 was under construction in the area around the time Tumolo disappeared. This theory has not been verified, but law enforcement currently in charge of investigating Tumolo's case believe it is a likely possibility.

Tumolo's parents are both deceased; his father died of cancer two years after his disappearance, and his mother in 2001. His older sister and Marino are still looking for him, however. His case remains unsolved.