"That's sinister, that's concerning. That's not somebody who is looking to take some cash, that's something more sinister," said James Kearney, captain of the Special Victim's Unit.
According to police, the crime happened on September 21 at about 10:30 p.m.
The man, who is believed to be in his late teens or early 20s, gained entry to a home on the 2500 block of S. 3rd Street by climbing through a second-story window.
While inside, the suspect rummaged through an empty room, stealing cash and a debit card. He then made his way into a second bedroom where 8 and 15-year-old sisters were sleeping.
Police said he sexually assaulted the teen victim.
"He touched my daughter and my daughter woke up. What happened? She doesn't know. She turned around and the guy is right there. Scary," said the victim's father.
When the victim moved, the suspect left the home and was last seen walking south on the 2600 block of S. Hancock Street, police said.
Along with cash and a debit card, the suspect stole a piggy bank from the girls' room. Their father says the ordeal has left them terrified.
"My younger one cries all night, scared," he said.
Kearney says he knows the surveillance is a little grainy, but he also knows this South Philly neighborhood and is confident someone will recognize the man.
The victim's father is asking that those with information step up.
"Who knows this guy? Talk to the police," he said. "I want him to go to jail."