One of the officers who helped save the boy, spoke out to Eyewitness News.
"He said his mommy was sick and he tried to help her, and we said, 'You did a great job buddy,'" said Police Officer Sylvia Dimenna, Union Township Police Department.
Police Officer Sylvia Dimenna and her partner were called to the home on Manor Drive because building management said there was a child locked in an apartment that had a strong order coming from it.
The door was locked with a chain, and they could see him standing there.
"He was naked, very thin, frail, he wasn't crying, he was just silent. When he was at the door Joe said, 'Listen buddy you have to stand over there,' and he did. He kicked in the door, I was right behind him. I scooped the child up and took him out into the hallway, right away. I went in and scooped him up and took him out of the environment," Dimenna said.
Dimenna, with 24 years on the force, says the child was wearing just one shoe he had put on the wrong foot.
She dressed him and later, in the hospital, he spoke, tentatively about his ordeal.
"He tried to help her, he said, 'I couldn't help Mommy. I tried to help her.' I think he probably tried to lift her up but couldn't help her," Dimenna said.
At the hospital, he ate for the first time in days.
"He likes grilled cheese. He likes grilled cheese sandwiches. The nurse got him a grilled cheese sandwich and he also had some Cheerios and milk. Thank goodness it worked out the way that it did and he ended up surviving," Dimenna said.
His mother, identified Wednesday as Kiana Workman, 38, of New York City's Brooklyn borough, was discovered dead Tuesday on the floor of her bedroom after maintenance workers at the apartment complex in northern New Jersey reported a foul odor. Because the chain lock was on, police said, the toddler couldn't get out.
Officer Joseph Sauer told the Associated Press, "The only way to describe the little boy was it was like a scene from World War II, from a concentration camp, he was that skinny. I mean, you could see all his bones."
The apartment in this city 15 miles west of New York belongs to Workman's mother, who is recuperating from surgery at a nursing center, said police, and they were working to speak with other relatives.
The boy, now in state custody, was treated for malnourishment and dehydration, but was released from the hospital on Thursday.
"Physically, he's fine. Whether there are any mental problems later on ... I'm not a child expert," Police Director Daniel Zieser said.
The boy was not strong enough to open the refrigerator and was unable to open a can of soup. Police said he told them he had been eating from a bag of sugar.
The boy could not say how long his mother had been dead.
Police said he put lotion on his mother, leaving behind handprints, in an attempt to help her.
Officer Dimenna, who traveled in the ambulance with the boy and stayed with him at the hospital, said he was very bright and articulate but tired.
"He said he missed his mommy," she said.
Police initially estimated she had been dead five days before the discovery was made, but Zieser said Wednesday it may have been two to three. Nobody had talked to her for about a week.
The boy weighed 26 pounds, but at the age of 4? should have weighed 40 pounds or more, Zieser said.
"It's possible he was improperly cared for before the mother's death; we just don't know yet," Zieser said.
Autopsy results that would help them better determine the time of death were pending. Police said they did not suspect foul play.
Police said they were getting calls from around the world from people offering to adopt the child or donate money or toys.
"It's overwhelming," Zieser said.
"I just hope everything works out for the child," the police director said. "We're just going to take it one step at a time and do the best that we can for the child."
Police said they were trying to find someone in the family capable of taking care of the boy, including a brother of Workman believed to live out West. But he said it would be up to the state's child welfare agency to determine where the child is placed.
Zieser described the apartment complex as a well-maintained property with few problems.
But he said everyone there "basically stays to themselves."
(The Associated Press contributed to this report)