In May of 2011, the disappearance of Timmothy Pitzen stunned the communities around suburban Chicago. Timmothy vanished after his mother, Amy Fry-Pitzen, took him out of an elementary school in Aurora, Ill., and drove him to Wisconsin, where they were last seen together at a water park.

Ms. Fry-Pitzen’s body was found soon after in a motel room in Rockford, Ill., after an apparent suicide. She left a note saying that her son, Timmothy, was now in safe hands with someone who loved him and that “You will never find him.”

An expansive search began for Timmothy, as his panicked, grieving family — including his father, James Pitzen — pleaded for help.

Posters went up in Illinois, Wisconsin, Iowa and beyond. Law enforcement authorities searched parks and woods across Northern Illinois with help from bloodhounds, planes and all-terrain vehicles. Family members passed out pictures of the boy — then 4-foot-2, with brown hair and brown eyes — in small towns in Illinois.

For months, the authorities followed clues, cellphone logs, email accounts and forensic evidence inside the vehicle that Timmothy had been in with his mother before he vanished. The boy’s car seat, which initially seemed to have gone missing when he disappeared, turned out to be with relatives all along. The authorities continued looking for a Spider Man backpack, which Timmothy was believed to have had with him on the day of his disappearance.

Over the years, sightings were reported, but none panned out. Renderings of what Timmothy might look like, accounting for aging, were created and distributed. Someone thought they saw him at a travel plaza in Dixon, Ill., but it turned out to be someone else. Another reported seeing a boy at a Denny’s in North Aurora, Ill. Yet another lead took the authorities to Massachusetts.