Michael Thomas Gargiulo was born on February 15, 1976, in Glenview, Illinois. He grew up in a suburb of Chicago, where he spent his early years.

Michael Thomas Gargiulo committed a series of brutal murders. The first known murder occurred in Glenview, Illinois, where he stabbed his neighbor, 18-year-old Tricia Pacaccio, on August 14, 1993. Her body was discovered by her father the next morning.

After moving to Los Angeles in 1998, Gargiulo killed two more women and attempted to murder another. On February 21, 2001, he murdered Ashley Ellerin, a 22-year-old woman, in her Hollywood home. She was stabbed 47 times, with severe wounds to her neck, chest, and back. Ellerin had a planned date with actor Ashton Kutcher that night.

On December 1, 2005, Gargiulo killed Maria Bruno, a 32-year-old neighbor in El Monte, California, stabbing her 17 times in her home. Later, on April 28, 2008, he attempted to murder Michelle Murphy, another neighbor, in Santa Monica. Murphy fought back, and DNA evidence linking Gargiulo was found at the scene.

Gargiulo was arrested on June 6, 2008, by the Santa Monica Police Department. In 2011, he was charged with the murder of Tricia Pacaccio along with the two murders in California. As the investigations progressed, police suspected he might have more victims, but he was only charged in connection with the three known murders.

His trial began on May 2, 2019, and on August 15, 2019, Gargiulo was found guilty on all charges. He received the death penalty on October 18, 2019. Sentencing in California was delayed multiple times, and he was eventually sentenced to death on July 16, 2021. He is expected to be extradited to Illinois for Pacaccio's murder if convicted there.