She said the teen was rubbing up against the child in the garage while the young boy's family was gardening in the backyard.
"He came in and said, 'Mom (he) was over there humping the little boy," the anonymous neighbor said.
Another neighbor said the teen was holding the young child.
"The boy had the little baby in his arms like he was holding him, and I look at him like, 'Put him down, he's a little kid,'" the other neighbor said.
The suspect is a 17-year-old who lives across the street. Parents say that teen tried to proposition the 6-year-old twice before.
"The second time he lured my son across the street and asked my son 'Can I hump you?' and my son said no and went and told his mother," the first parent said. "He keeps saying he's 13 years old and in the 8th grade but come to find out, he's 17."
Detroit police confirm the 17-year-old was taken into custody and there was a prior report about another incident. They also say the teen is possibly mentally handicapped.
The relatives of the three-year-old fear there's a predator in their midst and want him off the streets.
"I'm really mad I really think the prosecutor needs to hurry up with the situation because that's rape." the parent said.
The victim's family wants all parents to not only watch their kids but to speak up if something happens.
"They need to talk to their kid," the parent said. "They're on their phone, Facebook, and all that. They need to stop all that. You need to be on your kids and watch who they're around because it's dangerous."