"He was a wonderful young man doing everything he possibly could to pull himself out of this darkness," said Hamilton, who has sued the Catholic Church on behalf of alleged victims of priests. "It's a tremendous tragedy that he is gone."
Philadelphia District Attorney Seth Williams released a statement praising the man's courage in agreeing to press charges against Brennan.
"The decades-long demons and scars the victim in this case endured ended this weekend, when he was found dead by Philadelphia police detectives," Williams said. "This young man's courage should serve as an inspiration to us all."
Jeff Moran, a spokesman for the Medical Examiner's Office, said an autopsy concluded that the victim died of accidental "drug intoxication."
Williams said his office was reviewing the case against Brennan and would announce its decision next week.
Prosecution would be extremely difficult without a complaining witness, whose credibility before a jury is central to obtaining a guilty verdict. Even if an alleged victim's testimony were preserved in a video deposition, defense attorneys would challenge its use because of their inability to question the person.
Hamilton conceded that the allegations against Brennan will likely now never get before a jury.
Word of the death began to spread late Wednesday after the District Attorney's Office announced cancellation of Brennan's preliminary hearing, scheduled for Thursday.
Brennan's attorney, Trevan Borum, said he was told of the delay because of "the need for further investigation."
Borum said Brennan lives in Maryland and is ill with high blood pressure and cardiovascular disease, and for that reason did not object to the hearing's being continued to Nov. 14.
Borum declined to comment on the death.
Assistant District Attorney Evangelia Manos was not in court to personally request the postponement.
Sources said the family was "devastated" and that the young man had long struggled with drug problems.
That is not unusual for victims of sexual abuse, said David Clohessy, director of the St. Louis-based SNAP (Survivors Network of Those Abused by Priests).
"I would go so far as to say, 90 percent of the victims we have helped over the decades have responded to trauma through some sort of self-destructive behavior. . . . Something, anything, to try to numb the pain," Clohessy said.
Clohessy said SNAP staffers tell all who call to seek professional help "no matter how long ago the abuse happened, who the person was, or how well you think you are coping."
Clohessy praised the man for contacting authorities and said, "It is now more important than ever for people who have knowledge or suspicions about Brennan's crimes to take a deep breath, pick up the phone, and call the police."
Brennan's name was prominently mentioned in two Philadelphia grand jury reports on the sexual abuse of minors by priests in the Archdiocese of Philadelphia.
Brennan was never criminally charged. After the 2005 grand jury report, church officials ordered him to relinquish all priestly duties and retire. Brennan then moved to Perrysville, Md.
That changed after last year's trial of Msgr. William J. Lynn, the first Catholic Church official convicted for a supervisory role in covering up the conduct of pedophile priests.
Reportedly encouraged by Lynn's conviction and three- to six-year prison term, the man contacted archdiocesan officials in January.
That day, church officials called the District Attorney's Office and relayed the allegation that Brennan sexually abused the man from ages 11 to 14 at Resurrection of Our Lord Parish in Rhawnhurst.