Antonio Rodriguez was so quiet, so calm, that detectives questioning him about a string of rapes and strangulations barely could hear him at times.
Arrested Monday night after DNA linked him to the deaths of three women in Kensington last year, Rodriguez said in his confession that he didn't set out to kill and that he knew he had to stop, sources close to the investigation said.
His meek demeanor and his seemingly stable upbringing puzzled detectives and belied the brutality of the assaults that terrorized Kensington for months.
The 22-year-old, who grew up blocks from the neighborhood he has been accused of stalking, is being held on an outstanding bench warrant for a probation violation.
Though his DNA has been linked to evidence at all three crime scenes, Rodriguez will not be charged until police have confirmation from a second DNA swab taken after his arrest.
The test results were not available Tuesday, but they are expected soon.
A review of records and interviews with neighbors and police sources show a young man who avoided run-ins with the law while growing up in a good home, but who drifted into drugs as he reached adulthood.
Despite those troubles - a few months in jail and a felony drug conviction - nothing in his background indicated an escalation into sexual violence.
Detectives interviewed two girlfriends - one former and one current - who said he was never violent and never displayed any sexual issues, sources said.
Rodriguez did not know any of the victims - Elaine Goldberg, 21, Nicole Piacentini, 35, or Casey Mahoney, 27. He told detectives that he had met each on the street in Kensington and propositioned them.
He described wanting to have "rough fantasy sex" that included choking them unconscious but said he did not set out to kill the women, according to sources.
After the first deaths, at least three other Kensington women came forward to report encounters with a man who sexually assaulted, choked, or hit them. They did not immediately report the attacks, so no DNA could be collected.
Two of the women described their attacker as soft-spoken; one said he had carried a white iPod and called himself "Anthony." One woman said she was choked and might have been sexually assaulted while she was unconscious.
Special Victims Unit detectives are investigating Rodriguez to see if he is responsible for those attacks and possibly others, said SVU Capt. John Darby.
After Mahoney, the last homicide victim, Rodriguez told detectives that he didn't want to kill again, according to sources close to the investigation.
Rodriguez was born in Camden and sent to live with foster parents as an infant. The foster parents legally adopted Rodriguez and his twin brother when they were about 5 years old.
His adoptive family is Puerto Rican. Rodriguez, who is African American and known in the neighborhood as "Black," grew up speaking Spanish. He did not learn English until enrolling in school.
"He was always hyper," said neighbor Matthew Padro. "He liked to joke around a lot."
Padro said he played football with Rodriguez in the park a few times and used to see him at the local library after school, doing his homework.
As a young adult, however, Rodriguez started selling drugs on Mutter Street, around the corner from their Mascher Street block, Padro said.
"He was always hanging around down the block," Padro said. "The parents knew that he was getting into drugs. They didn't kick him out, but they tried to get tough with him. His dad told him he didn't want that stuff around here."
Padro described Rodriguez's parents as "real cool people, honest people." He said Rodriguez and his twin are identical, but people could tell them apart.
Rodriguez was arrested Monday night at a home in the 3300 block of Mutter Street, where he used to hang out.
"Everybody knew him on the block," said resident Gladys Martinez. "He used to play basketball with my son."
She said she knew him only as "Black," and didn't know his real name until she saw him on television Monday.
On Tuesday, a patrol car was parked in front of the house where he was arrested. Police said no one was in the home. Neighbors said squatters and drug dealers used the house.
"They take girls up in there. They get high in there," said a 48-year-old neighbor who did not want to identify himself. "This is a heavy drug block. You get junkies through here. . . . That's how the young girls get lured into these house. They're strung out."
Rodriguez had no juvenile record, but he was arrested twice in 2009 on minor drug-possession charges, receiving probation.
That was also the year Rodriguez was shot multiple times in the 3300 block of Gransback Street, about half a dozen blocks from his family's home.
He was minimally cooperative, and the case was never solved. The shooting left Rodriguez with a distinctive scar from his left earlobe to the middle of his throat, where a tracheotomy tube had been inserted.
On June 4, 2010, he was arrested on marijuana- and cocaine-distribution charges in the 100 block of East Willard Street, another nearby street known for drug dealing.
Rodriguez was housed at the Curran-Fromhold Correctional Facility until mid-August, when his bail was reduced. There was no record of his being assaulted or causing any trouble during his time in the Philadelphia jail system, records show.
On Oct. 21, he pleaded guilty to a felony drug charge and was sentenced to probation. A bench warrant was issued on Dec. 28 for violating his probation - the warrant on which he is being held.
Because he is a convicted felon, his DNA was collected when he pleaded guilty and sent to the state police to be entered into an offenders database.
Elaine Goldberg, the first victim, was found dead in a lot Nov. 3. Nicole Piacentini, the second victim, was found Nov. 13 at an abandoned building.
State police received DNA evidence collected from one of those victims Nov. 22 and uploaded it into the database the next day. No match was made because Rodriguez's DNA, which had arrived on Oct. 25, had not yet been entered into the database.
Because of a backlog, staffing shortages, and the need to upgrade computer servers, Rodriguez's DNA wasn't uploaded until Jan. 10. The match was made Monday morning, and police tracked him down and arrested him that evening.
In the meantime, Casey Mahoney, the third victim, was found dead on Dec. 15 in the woods along a set of railroad tracks.