INDIANAPOLIS -- Indianapolis police are investigating how a 19-month-old boy found wandering in only a diaper was able to leave his home late at night.

Neighbors found the boy near Rebecca Drive and Rockville Road just after 10:30 p.m. Wednesday, 6News' Stacia Matthews reported.

"It has a diaper on and it's running up and down the road ... It was screaming, scared, obviously," a caller told a 911 operator.

A short time later, the boy's grandmother called police, saying that her daughter, Samatha Hererra, had just gotten home and was looking for her son.

The boy's father, Charles Dickens, told police that he gave the child a bath and put him to bed, although he admitted that he may have left the front door ajar, investigators said.

Neighbors said they are concerned, but not shocked.

"It doesn't surprise me," said next door neighbor Ken Cooksey. "A lot of people let their kids wander and play ball in the street and stuff."

Police said it's important for parents to know where their children are as the weather gets warmer.

"Especially this summer, some of the fears that we always have are in some subdivisions with retention ponds and things like that," said Lt. Jeffrey Duhamell. "You just constantly have to be vigilant about watching where your children are."

The 19-month-old and his 9-year-old brother were in the custody of Child Protective Services on Thursday. Police said the case is under investigation.