The Suffolk County Police Department says it will review a September arrest of a man suspected in double murder in Bellport that they discovered after the suspect killed himself.

Police say William Farnum, 43, is believed to have killed his father James and sister Amanda, leaving their bodies in their Bellport home before leading police on a chase and slitting his own throat.

William Farnum was out on parole and had been arrested at least four times in the three months leading up to the killings.

Jennifer Harrison is a victim's advocate who used to work with Amanda.

"I just remember talking to her from time to time about her brother and the situation they were in, she was scared," says Harrison. "At first my heart broke, and then I got angry again that system had failed her and her family."

News 12's Eileen Lehpamer dug into what went wrong that led to a parolee still under state supervision to be arrested four times yet still be free. She dug through court records, spoke to parole officials, legal experts and more.

According to court records, Farnum was arrested July 15 on grand larceny, released for arraignment later and his parole officer was notified. He was then arrested two more times on Aug. 2 and 3, and was again issued desk appearance tickets.

It wasn't until Aug. 5 that the New York State Department of Corrections and Community Supervision issued a warrant for Farnum's arrest and updated the national database, known as NCIC. Then on Sept. 8, Suffolk police arrested Farnum again on charges of marijuana possession and resisting arrest. He was once again released on a desk appearance ticket, despite an active parole warrant for his arrest.

"Let's be clear, there is more than one way to determine whether or not someone has a warrant. One way is to run their name, another way would be to take their fingerprints," says criminal defense attorney Brian Griffin.

When asked what happened at the Sept. 8 arrest, a Suffolk police spokeswoman issued a statement, saying, "As part of arrest procedures, officers are to run criminal history and warrant checks. The department is currently reviewing the circumstances surrounding the arrest of William Farnum that occurred on Sept. 8."

Police have not released how James and Amanda Farnum were killed. The investigation is ongoing.