CHESTERFIELD, Mich. -- Police said they want to catch the man who brazenly groped a 13-year-old girl in a crowded store because they are afraid what he's capable of doing when people aren’t around.

Surveillance video from the Kohl's Department Store on Gratiot Avenue in Chesterfield Township Wednesday shows a man, believed to be in his 30s, groping the girl.

Watch: Girl Reports Being Grabbed By Man In Store

Detective Brian Chadwick of the Chesterfield Township police department said it appeared the man targeted the sisters.

"I believe he spotted them in the parking lot. He was probably waiting in the parking lot and spotted them and decided they were going to be his victim and followed them into the store," Chadwick said.

The man was seen on camera following around a 13-year-old girl and her 17-year-old sister for a few minutes before he pretended to trip and grabbed the young teen's rear-end.

Police said the man apologized to the girl in an attempt to make the incident appear as though it was an accident. But police said they believe the man deliberately touched the girl because he made sure to stand in their path. Police added that the man didn't just caress her behind, but grabbed her.

Detective Chadwick said the victim was troubled and angry over the incident.

"I think the victim was pretty certain that it was deliberate because of the kind of contact that he made with her," Chadwick said.

When the teens told their mother about it, police were called and an investigation was launched.

The man is described as a white, in his late 30s to early 40s,with dirty blond hair and a goatee, about 5 feet 6 inches, medium build, and was wearing a blue jean shirt and jeans.

If anyone recognizes the man in the surveillance video, you are asked to call the Chesterfield Township Police at 586-949-2322.