Mackerley came home from school and told his babysitter that he was going to walk two doors from his family's house in the 300 block of Chew Street to play with friends during the afternoon of June 7, 1984 in Allentown, Pennsylvania. Witnesses observed Mackerley walking between Fourth Street and Gordon Street about a block from his second-floor apartment home in the 360 block of Chew Street, but what happened to him afterwards is unclear.

The owner of Marco's Doggie Shop, a local hot dog stand, stated that Mackerley came in at 4:00 p.m. and spent approximately 45 minutes browsing around the store. Mackerley told the shop owner that he was in the store to avoid some teenaged boys who were chasing him. He left at 4:45 p.m. and walked east on Gordon Street that afternoon. His parents believe he may have been headed for the Chew Street home of an elderly woman he liked to visit. The two boys who were chasing Mackerley that day were later interviewed by law enforcement and are not thought to have been involved in his disappearance.

Another witness claimed to have seen Mackerley talking to an unidentified man and woman in a park near Jordan Creek, approximately one block from his residence, at approximately 4:30 p.m. This area was about one block away from Mackerley's residence; the story was not confirmed, but it has not been ruled out as a possible scenario either. Mackerley has never been heard from again.

Mackerley's parents did not report him missing until 11:10 p.m. that evening. His mother had been in the hospital undergoing surgery, and he was in the care of an aunt at the time of his disappearance. He liked to stay out late and usually did not return home until about 9:30 p.m. Once he left the house in the early morning hours and accidentally locked himself out; his parents installed a special lock on the door to prevent this event from occuring again. When Mackerley did not come home late in the evening of June 7 and did not answer parents' calls for him, they contacted police. An extensive search of the area turned up no clues to his whereabouts.

Mackerley enjoyed playing near water, particularly near Jordan Creek and Lehigh River, at the time of his disappearance. Shortly before he vanished he mentioned that he would like to visit Dorney Park. No trace of him was found at any of those places. His parents took lie detector tests early on in the investigation and were ruled out as suspects in their son's disappearance. There were rumors that they had abused and/or neglected Mackerley, but the Social Services investigated and found the allegations to be without merit. Mackerley's parents have three other children, two boys and a girl; he is their second-oldest child.

In January of 1984, Mackerley told his parents, his school's nurse, and a psychologist that he had been molested by a couple named Frank and Elizabeth. His accounts of the alleged incident differed; once he said he had been molested on the railroad tracks near Jordan Street and the Lehigh River and other times he said Frank and Elizabeth had driven him to an apartment in Allentown and molested him there before taking him back to his own neighborhood. There may have been more than one incident. Mackerley says the couple threatened to hurt him if he told anybody about what they had done. The Allentown police were notified but could not find enough evidence to warrant an investigation, as Mackerley could not provide any last names or addresses in his accounts. It is not known whether molestation(s), if they actually happened, have anything to do with Mackerley's disappearance six months later.

In 1988, David Riggs, a self-proclaimed private investigator from New York who claimed to have founded an organization called Search Seven to look for Mackerley and other missing children, was arrested in West Virginia after he accosted five young boys and offered to pay them to pose wearing bikini underwear. None of the boys took him up on the offer. Riggs pleaded guilty to two counts of attempted child abduction and one count of sexual abuse in connection with the incidents and was sentenced to a year in prison. Investigators looked into the possibility that Riggs was involved in Mackerley's abduction, but they found no evidence indicating this and he was eventually ruled out as a suspect. He was at one time a doctoral candidate at Columbia University. He has previously served time in prison but not for child abuse-related crimes. Riggs does not have a private investigator's license in New York and the organization he had supposedly founded, Search Seven, is not registered as a non-profit corporation in that state.

Eleven months after Mackerley disappeared, his family moved into the house in the 390 block of Chew Street that he liked to visit. The elderly female friend of Mackerley's who had lived there was moving to a retirement home and Mackerley's family wanted to be at a place he knew and might return to. He had often played at the residence and had dreamed of living there someday. Mackerley's parents were unable to make the mortgage payments for the home, in spite of contributions from community members who were moved by their plight. They filed for bankruptcy and moved to Effort, Pennsylvania in 1989. The Chew Street residence has been vacant since that time.

Mackerley is described as friendly and talkative but a loner and a timid child who was afraid to sleep alone. He had a short attention span and had trouble writing and paying attention in school. Because of this, he was due to enter a class for learning-disabled students in the fall of 1984. Mackerley was born near Stanhope, New Jersey and moved to the Allentown area in June of 1983, a year before his disappearance. His case remains unsolved; he is believed to have been abducted by a non-family member. His parents believe he may be alive and not remember who he is. His case was re-opened in 2004, twenty years after his disappearance.