Andrew Urdiales's childhood remains largely a mystery, with little information available about his early years. However, a dark and disturbing event from his youth is well-documented. In June 1977, just before he turned 13, Andrew committed a horrifying act by beating the family dog to death with a baseball bat. He then lied to his parents, claiming the dog had been fatally injured in a fall.

Despite this troubling incident, Urdiales went on to complete his education, graduating from Thornridge High School in Dolton, Illinois, in 1982. Shortly after finishing high school, he decided to join the United States Marine Corps. This decision marked the beginning of a significant chapter in his life.

From 1984 to 1991, Urdiales was stationed at the Marine Corps Base Camp Pendleton in California. During his service, he underwent rigorous combat training and specialized as a radio operator at the Marine Corps base in Twentynine Palms. His military career included a deployment during Desert Storm, adding a notable element to his time in the Marine Corps.

Andrew Urdiales committed his first murder on January 18, 1986. At Saddleback Community College in Mission Viejo, California, he stalked and attacked 23-year-old Robbin Brandley, a communication arts student. He stabbed her 41 times with a knife, leaving her dead. Two years later, on July 17, 1988, he killed 29-year-old Julie McGhee, shooting her with a .45 caliber pistol and leaving her body in a ditch near Cathedral City, California. That September, he struck again, murdering 31-year-old Mary Ann Wells in San Diego. Her body was found in an abandoned warehouse. His next victim was 18-year-old Tammie Erwin, whom he killed in Palm Springs on April 17, 1989.

In 1991, after being honorably discharged from the Marine Corps, Urdiales moved back to his parents' home in Chicago.

However, he returned to California in September 1992. On September 27, 1992, he met 19-year-old nurse Jennifer Asbenson, who needed a ride to work. After giving her a ride, he asked for her phone number, which she gave falsely. When she finished her shift, Urdiales was waiting for her and offered her another ride, which she accepted. During the drive, he confronted her about the fake number, assaulted her, tied her hands, and cut off her clothes. Although he attempted to rape her, he couldn't. Asbenson bravely called him a "coward" and begged for her life. Urdiales bit her neck, beat her, and locked her in the trunk of his car. She managed to untie her hands, escape from the trunk, and ran down the highway. Urdiales chased her with a machete, but she was able to flag down a truck with two marines. Urdiales fled, leaving behind only the bite mark as evidence.

After three years without killing, fearing capture, Urdiales returned to California in March 1995. He encountered 32-year-old sex worker Denise Maney in Cathedral City, forced her into his car, drove her to the desert, and shot her. He left her body for scavengers. Urdiales continued his spree, crossing into Bloomington, Indiana, in April 1996, where he murdered 25-year-old Laura Ulyaki. 

Her body was found on April 14 in Wolf Lake, Illinois. On July 14, 1996, police found the body of 21-year-old Cassandra Corum in the Vermilion River, and on August 2, 1996, they found 22-year-old Lynn Huber's body in Wolf Lake. Urdiales was finally arrested on April 23, 1997, when police wanted to check his gun in connection to the murders. He confessed to all eight murders, and ballistics tests confirmed his involvement.

Andrew Urdiales was tried and sentenced to death multiple times. In Illinois, his first death sentence was commuted to life imprisonment in 2003 by Governor George Ryan. Urdiales continued to face legal battles, and despite claiming mental illness, he was re-sentenced to death in 2004. However, in 2011, Illinois abolished the death penalty, commuting his sentence again to life in prison. California then sought to extradite him, and on May 23, 2018, he was convicted of five murders in Southern California. He received a death sentence for the third time on October 5, 2018. On November 2, 2018, Urdiales was found dead in his cell at San Quentin State Prison, having apparently committed suicide by hanging. He was 54 years old.