Jan. 20, 2011 -- The man who has confessed to being Philadelphia's "Kensington Strangler" claims he didn't mean for the women to die, but experts on what they call sexual, serial killers believe the suspect knew what he was doing and "enjoyed the act of killing them."
Sources told ABC Affiliate WPVI that Antonio Rodriguez has confessed to police that he murdered Elaine Goldberg, Nicole Piacentini and Casey Mahoney between November and mid-December of last year. Prosecutors have approved charges to be filed against Rodriguez today. He is expected to be formally charged with three counts each of murder, rape, involuntary deviate sexual intercourse and abuse of a corpse.
Rodriguez is also a suspect in the sexual assault of at least three other women.
The 22-year-old suspect is described as soft spoken and at 5-feet-9 and 150 pounds is slightly built.
Police sources told the Philadelphia Inquirer that during his interrogation, Rodriguez said that he didn't set out to kill the women and that he knew he had to stop.
Rodriguez wanted to have "rough fantasy sex," choking the women until they were unconscious, but he did not want to kill them, sources told the Inquirer.
Forensic psychologists told ABC News that Rodriguez, if convicted of being the Kensington Strangler, fits the profile of a sexual, serial killer.
Forensic psychologist Louis B. Schlesinger said that sexual, serial killers often choose strangulation as the method of their murder because it's up close and personal.
"Strangulation allows an individual to control the speed at which the victim dies and this is very sexually stimulating for him," Schlesinger said. "It's not uncommon to strangle until almost the point of death, then release the pressure as she [the victim] is about to die so so he can increase the time of the sexual strangulation."
Dr. James Alan Fox of Northeastern University who has written five books about serial killers, said sexual serial killers are uniquely sadistic murderers and Rodriguez's claim that he didn't mean to kill the women is not convincing.
"He certainly knew that choking could lead to death... It may not mean that having them dead was his purpose…but he certainly enjoyed the act of killing them and overpowering them through strangulation," Fox said.
Most serial killers who fit the pattern of behavior for the Kensington Strangler are between the ages of 25 and 35, Schlesinger said.
"He didn't wake up one day...this began 10, 15 years ago in his mind, in his fantasies and so eventually he then acted out," Schlesinger said.
Kensington Strangler Unique For Crossing Racial Lines In Killings
Some serial, sexual killers like Gary Ridgway, dubbed the Green River Killer, are able to elude authorities for dozens of years.
Ridgway was arrested in 2001 in Washington state for killing dozens of women by strangling them. Four of his victims were found in the Green River.
"Some individuals can plan crimes and elude law enforcement for a significant period of time...others act out in an impulsive way. The crime is unplanned, there's a lot of evidence left behind and they typically get apprehended more quickly," Schlesinger said.
The Kensington Strangler left behind DNA evidence that eventually led to his arrest. DNA results from a previous conviction on drug charges pointed to Rodriguez. Fresh DNA results taken after his arrest also linked him to the murders.
What stands out about the strangler, if it is Rodriguez, is that he crossed racial lines in choosing his victims.
"If in fact the person arrested is the killer, it would be unusual to have serial killings across racial lines," Fox said. "Most white killers kill white victims and black killers kill black victims."
None of the victims murdered were African American, like Rodriguez.
"Serial killers are motivated by sexual fantasy and sadism and have a particular type that they're attracted...It's a crime of selection and killers will pick and choose," Fox said.
Sources have described Rodriguez as a mild-mannered, quiet guy who didn't stand out.
Forensic psychologists said that serial killers often fly under the radar.
"They don't look and act like our stereotype of a serial killer...If someone looked and acted bizarre, if someone looked like Jason from 'Friday the Thirteenth,' we'd avoid them. Part of the way a serial killer operates is they look so extraordinarily ordinary," Fox said.
"This is not about being stark raving mad," said Dr. N.G. Berrill, director of New York Center for Neuropsychology and Forensic Behavioral Science. "This is not being a lunatic. This about cultivating this sadistic and predatory instinct. If you're not a victim, you don't know about it."
One of the things that helped catch the alleged suspect is that he may have left some victims alive, forensic psychologists said.
Kensington Strangler Was 'Quiet'
In early October, a 30-year-old woman was choked to the point of unconsciousness in the same spot where one of the victim's bodies was found.
She came to the police after the murder of the first victim in November. She helped police generate a sketch of the man believed to be Rodriguez.
"There's three other assaults in the area that kind of fit the pattern of the homicide and the results of that are still pending," Lt. Ray Evers from the Philadelphia Police Department said. "At this time, they're still open investigations."
Police sources told WPVI that two of those victims have positively identified Rodriguez from his mug shot.
Some of the alleged victims had previously described the "Kensington Strangler" as having a quiet voice and referring to himself as "Anthony."
Rodriguez grew up blocks from the Kensington neighborhood that became the scene of the strangling deaths of the women. All of the women's bodies were found in a 10 block radius of one another.
The African American man was adopted by a Spanish-speaking family as a child, the Philadelphia Inquirer reported. He had no arrests as a minor, but turned to drugs as he entered adulthood.
Rodriguez spent time in jail in the summer of 2010 before being convicted in October 2010 on felony drug charges. He was sentenced to one year of probation just weeks before the murder of Eileen Goldberg on Nov. 3, 2010.
Eileen Goldberg's father, Joe Goldberg, is relieved that the "Kensington Strangler" may have been caught.
"I was happy to see him arrested," Goldberg said. "I was pleased to see him off the street because...it was intolerable on a daily basis that the guy who killed my daughter is out free as a bird and quite possibly getting ready to kill his next victim."
Goldberg called Rodriguez's statement to investigators that he didn't mean to kill the women "idiotic."
"I don't buy that. To choke the life out of somebody, you've got to be squeezing their neck for a considerable amount of time. If it's something that you didn't want to do, there was plenty of time not to do it," Goldberg said.
Eileen Goldberg, a 21-year-old nursing student, had struggled with prescription drug addiction, but had recently celebrated 30 days of sobriety before her murder.
"She was preaching the gospel of recovery," Goldberg said. "He snatched her life away before she ever had a chance to get married, have a baby, become what she wanted to be."
The Associated Press contributed to this report.