McFadden said police obtained Brown's DNA, which will be tested against evidence recovered from the four rapes.
The charges against Brown include four counts each of rape, aggravated assault, and kidnapping, all felonies. Lesser charges include weapons violations and corruption of a minor.
Brown was taken into custody less than 48 hours after police announced that one man was likely behind all four attacks. Police said the rapist approached each girl on the street with a gun before assaulting her in a more secluded area, such as a driveway. The girls' ages range from 12 to 17.
All of the attacks occurred within blocks of Brown's house. The rape of the 12-year-old girl occurred on a March morning while she waited for a school bus, police said. In the following months, police said, the rapist struck twice on East Chelten Avenue - two short blocks from Brown's house - and on Wister Street, about a half-mile from his house. The last attack occurred early Sunday.
A phone call to Brown's house was not returned. A woman who identified herself to CBS3 as Brown's mother said her son was not the rapist. She said a "paranoid" neighbor called the cops.
The woman said detectives removed her son's bike as part of the investigation. Police have video of the rapist riding a mountain bike before and after one of the attacks.
"My son works every day," the woman told CBS3. "He has a girlfriend that lives here. What he got to run out and rape something for? And all his time is accounted for. He's at work or home."
Contact Ben Finley at 215-854-2611 or firstname.lastname@example.org.