While working at Adventist Health Glendale in California, Saldivar harmed his patients by injecting them with a paralytic drug that caused them to stop breathing or their hearts to stop. He had drugs like morphine and suxamethonium chloride, along with used and fresh syringes in his locker. Specifically, he used Pancuronium, a drug typically used to stop breathing before a patient is placed on a ventilator, in six of the cases. Saldivar chose victims who were already unconscious and nearing death, making it hard to detect any pattern in the death rates during his shifts. This lack of a noticeable pattern made it difficult to connect the deaths to him and slowed the investigation.

His job at the hospital ended on March 13, 1998. Soon after, he confessed to 50 murders, a statement he later took back. To gather strong evidence, the police exhumed bodies of patients who had died during Saldivar's shifts and had been buried instead of cremated. They were looking for high levels of Pancuronium, which can be detected in the body for many months. Of the 1,050 patients who died while Saldivar was working, 20 bodies were exhumed, and six of these showed lethal levels of the drug. Medical records confirmed that Pancuronium was not prescribed by doctors to these patients.
 

On March 12, 2002, Saldivar, then 32, pleaded guilty to six counts of murder and received seven consecutive life sentences without parole. He is serving his time in California State Prison in Corcoran.

Initially, in 1998, Saldivar told the police he had ended the lives of up to 50 patients and contributed to the deaths of 100 to 200. He later claimed to have killed at least 60 patients by 1994 and admitted he "lost count" after that but continued his actions for three more years.
 

Sergeant John McKillop of the Glendale Police Department led the investigation, supported by Adventist Health Glendale. Although statistical analysis suggests Saldivar could have committed as many as 200 murders, confirming this number is challenging due to many bodies being cremated or the effects of time on the evidence.