Bardo was the youngest of seven children. His mother was Korean and his father was a noncommissioned officer in the U.S. Air Force. The family moved frequently and eventually settled in Tucson, Arizona in 1983. Bardo reportedly had a troubled childhood. He was abused by one of his siblings and placed in foster care after he threatened to commit suicide. Bardo's family had a history of mental illness, and he himself was diagnosed with manic depression. At the age of 15, he was institutionalized for a month for emotional problems. Bardo dropped out of Pueblo Magnet High School in the ninth grade and began working as a janitor at Jack in the Box.
In the 18 months prior to Schaeffer's murder, Bardo had been arrested three times on charges including domestic violence and disorderly conduct. Neighbors of Bardo also said that he had exhibited unexplained strange and threatening behavior towards them.
Prior to developing an obsession with Schaeffer, Bardo had stalked child peace activist Samantha Smith before her death in a 1985 plane crash. After writing numerous letters to Schaeffer, Bardo attempted to gain access to the set of the CBS TV series My Sister Sam, on which Schaeffer played a starring role. Ultimately, he obtained her home address via a detective agency, who in turn tracked it via California Department of Motor Vehicles records. On July 18, 1989, he confronted her at her home, angry at her for having starred in a sex scene in the film Scenes from the Class Struggle in Beverly Hills; in his eyes, she had "lost her innocence." He visited her at her apartment and told her he was a big fan. She signed an autograph, went back into her apartment and he left. About an hour later, Bardo again rang the bell to her apartment. Upon Schaeffer opening the door, Bardo fired one round of ammunition, killing her. Bardo was later arrested when observed walking aimlessly in traffic.
The prosecutor for the state was Marcia Clark, who later became known as a lead prosecutor in the O. J. Simpson murder trial. Bardo was housed in a Sensitive Needs Unit (SNU) for inmates such as gang members, notorious prisoners, and those convicted of sex crimes. During the trial, Bardo claimed the U2 song "Exit" was an influence in the murder; the song played in the court room as evidence (with Bardo lip-synching the lyrics).
Bardo's attorneys conceded that he had murdered Schaeffer, but argued that he was mentally ill. Psychiatrist Park Dietz, testifying for the defense, said that Bardo had schizophrenia and it was his illness that led him to commit the murder. Bardo was found guilty of first degree murder and sentenced to life imprisonment without the possibility of parole.
Bardo carried a red paperback copy of The Catcher in the Rye when he murdered Schaeffer, which he tossed onto the roof of a building as he fled. He insisted that it was coincidental and that he was not emulating Mark David Chapman, who had also carried a copy with him when he shot and killed John Lennon on December 8, 1980.
As a consequence of Bardo's actions and his methods of obtaining Schaeffer's address, the U.S. federal government passed the Driver's Privacy Protection Act, which prohibits state Departments of Motor Vehicles from disclosing the home addresses of state residents.
On July 27, 2007, Bardo was stabbed 11 times on his way to breakfast in the maximum-security unit at Mule Creek State Prison in Amador County, California. Two inmate-made weapons were found at the scene. He was treated at the UC Davis Medical Center and returned to prison, officials said. The suspect in the attack was another convict, serving 82-years-to-life for second-degree murder.
As of 2017, Bardo is serving his life sentence at the Ironwood State Prison in Blythe, California.