The boy told police he went to the apartment overnight and told the person who lives there that his parents weren’t at home.
The apartment is less than 100 yards away from his.
Police said officers had been going door-to-door looking for Justin.
Update 9:15 a.m. EST Nov. 30: Police said Justin was found alive and safe around 9 a.m.
No other details were immediately released.
Original report: Maj. Mike Smathers said the boy was last seen around midnight at his apartment. He said the child was in the apartment with his mother, two other younger children, and two teenagers or young adults.
His mother told police she thought she heard Justin get up to go to the bathroom. She fell back asleep and then realized her son was no longer in the apartment.
Family members looked on their own for roughly 30 minutes before calling the police, Smathers said.
Smathers also said Justin does not speak English but does recognize his name when he hears it. The boy does not have any disabilities or cognitive issues that police have been made aware of.
Smathers said the biggest challenge police are facing is a language barrier with the family, and that Spanish-speaking detectives were called to help with interviews. He said the family is cooperating.
The entrance to the apartments was blocked by police, who had set up a mobile command post as they searched for Justin.
The boy is described as having short black hair and was last seen wearing a gray shirt, a green Teenage Mutant Ninja Turtles sweater, khaki pants, and black and brown shoes with white laces.
Authorities used a bloodhound to try to track Justin but were unsuccessful. Police also deployed their helicopter over the neighborhood to help in the search. The aircraft has a heat-sensing device, and firefighters were using handheld devices to check all the bodies of water in and around the complex.
Smathers said police were worried about the cold temperatures overnight and said all resources available in the county were being used to find the boy.
"This is a full-court press from our department," he said. "All the resources in this county have been brought to bear for this child."
Anyone with information about the boy is asked to call 911 immediately.