The so-called "pantless rapist," accused in the brutal sexual assault of a woman waiting for a bus near police headquarters in Center City, has been extradited back to Philadelphia from Mexico.

The FBI said 37-year-old Alberto Isaac Navarrete Suarez, also known as Dario Gomez Lopez, was returned to the United States on Monday night to face charges.

He had been in custody in Mexico City, awaiting extradition, since April 2012. Detectives tracked down Suarez's family members in Mexico, ultimately leading to his apprehension there, authorities said.

Suarez is facing charges in the Philadelphia case, as well as an alleged rape in western Pennsylvania. Federal authorities had also been seeking him, on a charge of unlawful flight to avoid prosecution for the rapes.

In the Philadelphia case, he is accused of raping, choking and beating a woman who was waiting for a SEPTA bus at 8th and Race streets.

"It was a brutal assault," Lt. Anthony McFadden of the Special Victims Unit said at a news conference this morning. The woman nearly lost consciousness before a passerby interrupted the assault and called 911, he said.

In the days after the Aug. 29, 2010, attack, Suarez was dubbed the "pantless rapist" because he fled the scene without his pants after hearing sirens from approaching police vehicles.

Suarez allegedly dragged the 22-year-old victim to a secluded area, where he choked and raped her, police said at the time of the incident. Surveillance video showed the assailant sprinting away barefoot, clad in a shirt and underwear, his pants left behind.

A Mexican driver's license left at the scene turned out to be a fake.

But detectives recovered a camera at the scene with photos of Suarez that led them to his house in South Philadelphia, McFadden said. From there, investigators were pointed toward a phone chain that Suarez had used to seek employment, McFadden said - and were able to track him to Texas.

But he eluded authorities and escaped across the border.

A warrant was later also issued for him in Allegheny County, charging him with a March 2010 kidnapping, rape and robbery of a teenage girl in Pittsburgh.

"He knew he was in trouble in Pittsburgh" and fled to Philadelphia, said Edward Hanko, special agent in charge of the FBI's Philadelphia office. Authorities said Suarez was believed to have spent about four or five months in Philadelphia, mostly working as laborer.

DNA evidence between the Philadelphia and Pittsburgh cases is a match, authorities said. McFadden said the physical evidence from the Center City rape hasn't been matched to any other unsolved sexual assaults in the city.

Hanko said the judicial system in Meixco "works much, much slower" than in the United States, leading to the two-and-a-half-year gap between his arrest and extradition. The process in Suarez's case, he said, took an especially long time because Suarez is a Mexican national, not a U.S. citizen.

The FBI said Suarez was handed over to the Philadelphia police's Special Victims Unit after arriving in the country on Monday.

Officials acknowledged that upcoming court proceedings in Philadelphia could both bring closure and new pain for the victim.

"It's bittersweet," McFadden said. "She had four years of trying to get some closure, some relief. Now, unfortunately the wounds are going to be reopened again."