Sanchez was born in San Sebastián, Puerto Rico. His family moved to the United States when he was 2 years old. His father died when he was young, and his mother remarried. Sanchez grew up in Florida before moving to the Buffalo area. He has one brother and two sisters. An aunt described him as a serious, quiet, and nice kid.

Sanchez worked as a machinist and factory worker at the American Brass Company plant on Military Road in Kenmore/Buffalo area. He worked afternoon and night shifts. He lived in the Cleveland Hill neighborhood of Cheektowaga, New York.

Sanchez was married to Kathleen and had two adult sons. He was a basketball coach for his sons' team at their school in Cheektowaga and also coached their Little League Baseball team. He enjoyed playing golf and gardening, living what seemed like a regular life. Sanchez registered to run in the annual Linda Yalem Safety Run at the University at Buffalo, a run dedicated to one of his murder victims.

Sanchez was active in his community and well-liked by his neighbors, who called him "Uncle Al." When Sanchez started his crimes, he strangled and killed his victims using a rope or cord. He also beat and/or raped them, and many victims fought back.

In later years, Sanchez used a ligature, wire, or garrote to strangle and suffocate his victims. Before his arrest, DNA evidence showed the Bike Path Killer was of Hispanic descent, and an FBI profiler said the killer frequented sex workers. Sanchez was arrested in 1991 and 1999 for soliciting prostitution. Once, he even solicited prostitution from an undercover police officer for $25 and was fined $75.

Linda Yalem was a sophomore at the University at Buffalo studying communications and training for the New York City Marathon. She was raped and killed on September 29, 1990, along the Ellicott Creek Bike Path. Majane Mazur was a known sex worker. She was murdered in November 1992 near the Amtrak rail line in downtown Buffalo.

Joan Diver was a nurse, the wife of a University at Buffalo chemistry professor, and a mother of four. She was murdered by blunt force trauma on September 29, 2006, exactly 16 years after Linda Yalem. Her body was found on a bike path in Newstead, New York, on October 1, 2006. Sanchez got the nickname "Bike Path Killer" because some of his crimes took place near secluded bike paths.

The murder of Linda Yalem in 1990 was investigated by the Amherst Police Department. The murder of Majane Mazur in 1992 was handled by the Buffalo Police Department. After Joan Diver's murder in 2006, a special task force called the Bike Path Task Force was formed by the Erie County Sheriff's Office, which included the New York State Police, Buffalo Police Department, and Amherst Police Department, with support from the FBI.

DNA found at eight crime scenes matched DNA secretly taken from Sanchez before his arrest. The police obtained Sanchez's DNA from silverware, a glass, and a napkin he used at a Latin American restaurant on January 13, 2007. These items were tested and matched the DNA from the Bike Path Killer.

On January 15, 2007, a police task force arrested Sanchez and charged him with the murders of Yalem, Mazur, and Diver. An Erie County grand jury indicted Sanchez for the murders of Yalem and Mazur on January 19, 2007. On May 17, 2007, Sanchez pled guilty to the murders in a surprise confession.

On August 15, 2007, Sanchez was sentenced to 75 years to life in prison by New York State Supreme Court Justice Christopher J. Burns. He was imprisoned at the Clinton Correctional Facility in New York. Sanchez was found unresponsive in his cell with a self-inflicted cut on his arm. He was taken to a hospital and pronounced dead on September 22, 2023, at age 65.

Anthony Capozzi was wrongly convicted and served 22 years in prison for two rapes committed by Sanchez. After Sanchez's arrest, investigators realized the crimes were similar and in the same area. DNA evidence linked Sanchez to the rapes, proving Capozzi's innocence. Capozzi was freed in March 2007 and later settled a civil lawsuit for $4.25 million. A law called Anthony's Law was introduced to expedite such lawsuits.