J. C. X. Simon was born around 1946 in the United States. Very little is known about his personal background with no public record confirms his exact date of birth, childhood, or early life. By the early 1970s, however, Simon had become heavily involved in extremist Black separatist ideology and was working at the Black Self-Help Center in San Francisco.

Simon was known for adopting a militaristic appearance and reportedly followed a strict moral code within the Death Angels—a shadowy, cult-like offshoot group believed to be operating within or adjacent to the Nation of Islam. Members were allegedly rewarded for murdering "white devils" or "dissident Blacks," and could earn "wings" as status symbols for carrying out successful executions.

Simon’s involvement in the Zebra Murders places him at the core of the Death Angels' operations. From October 1973 to April 1974, the group murdered at least 15 people and attempted to kill several more in a campaign of racially motivated violence. Most victims were selected at random and shot at close range with .32 caliber pistols.

The group operated under a rigid structure, some members planned, while others carried out the hits. Simon, along with Manuel Moore, Larry Green, and Jessie Cooks, were named as the most active killers.

According to Anthony Harris, the prosecution’s key informant, Simon attended multiple planning sessions where targets were discussed and assigned. He was later indicted for the murders of Tana Smith and Jane Holly, two women gunned down during the spree. Simon was also charged with the assault on Roxanne McMillan, a young woman who survived a shooting on the same night. The attacks all occurred on January 28, 1974, part of a chilling evening where four people were murdered and another gravely wounded in the span of just 90 minutes.

Simon was also stopped by police multiple times during the investigation, including once shortly after an abduction, but was released due to lack of evidence at the time. This would later fuel public outcry over police handling of the case.

Following Harris' tip, Simon was arrested on May 1, 1974, and charged with two counts of first-degree murder and multiple counts of assault with deadly weapons. During the year-long trial, evidence included ballistic matches to a .32 caliber pistol, Harris’ detailed testimony, and physical items found during searches of the Black Self-Help Center.

On March 12, 1976, J. C. X. Simon was convicted and sentenced to life in prison. His reaction during the verdict was emotionless, though co-defendants laughed as the jury read its decision.

Simon spent nearly four decades in custody at San Quentin State Prison. On March 12, 2015, exactly 39 years to the day after his conviction, he was found unresponsive in his cell. He was declared dead shortly after. No foul play was reported; the cause of death was listed as “unknown pending autopsy,” though he was 69 years old at the time and had been suffering from declining health.

Simon never expressed remorse and never publicly spoke about the crimes.