Ervil Morrell LeBaron was born on February 22, 1925, in the United States. His family practiced polygamy, a belief once part of the early Mormon teachings but later abandoned by the mainstream Church of Jesus Christ of Latter-day Saints (LDS Church). To escape U.S. laws against polygamy, the LeBaron family moved to northern Mexico in 1924 and established Colonia LeBaron in Galeana, Chihuahua.

After the death of their father, Alma Dayer LeBaron Sr., in 1951, a power struggle broke out between Ervil and his brothers. In 1955, Joel LeBaron founded the Church of the Firstborn of the Fulness of Times, with Ervil as his second-in-command. Their group attracted several families and established communities in Utah and Baja California, Mexico. Over time, Ervil became power-hungry an

In 1972, Ervil split from his brother's church and started his own group, the Church of the Lamb of God. He preached blood atonement, a belief that certain sins could only be forgiven through the sinner’s death. Soon, he began using this doctrine to justify killing his rivals.

That same year, he ordered the assassination of his own brother, Joel LeBaron. Joel was shot and killed in Ensenada, Baja California, Mexico. Ervil was arrested in Mexico for the murder, but the conviction was overturned, allowing him to go free. This marked the beginning of a deadly campaign against his enemies, both within his own group and in other polygamous sects.

One of his most notorious crimes was the murder of Rulon C. Allred, the leader of the Apostolic United Brethren, another Mormon fundamentalist sect. On May 10, 1977, Ervil’s 13th wife, Rena Chynoweth, and his stepdaughter, Ramona Marston, carried out the assassination, shooting Allred in his chiropractic office in Salt Lake City, Utah. Although Chynoweth was later acquitted, she later admitted to the murder in her memoir, "The Blood Covenant" (1990), describing the fear and control Ervil had over his followers.

Ervil also turned against members of his own family. His 10th wife, Vonda White, was convicted for killing Dean Grover Vest, a follower who wanted to leave the group. She also confessed to murdering Noemi Zarate Chynoweth, the wife of Ervil's father-in-law, Bud Chynoweth. His daughter, Rebecca LeBaron, was found dead in April 1977. She was 17 years old, pregnant with her second child, and had been strangled. It was believed that Ervil ordered her death after she tried to escape the cult.

On June 1, 1979, Ervil was arrested by Mexican authorities and extradited to the United States. In 1980, he was convicted of ordering the murder of Rulon C. Allred and sentenced to life in prison. However, his reign of terror did not end there. Before his death, he wrote a 400-page document called "The Book of the New Covenants," which listed people he wanted killed. His followers treated it like scripture and carried out more assassinations even after he was gone.

Ervil LeBaron died in his prison cell on August 16, 1981, from what was reported as natural causes. But his influence did not die with him. On June 27, 1988, a group of his loyal followers carried out a series of murders known as the "4 O'Clock Murders," killing four people across different locations in Texas. Five people, including his children and followers, were later convicted for these crimes. The last suspect, his daughter Jacqueline LeBaron, was arrested in May 2010 and pleaded guilty to conspiracy charges.

Ervil’s story has been the subject of many books, documentaries, and a 1993 TV movie, "Prophet of Evil: The Ervil LeBaron Story." In 2024, the documentary series "Daughters of the Cult" explored his life through the experiences of his former followers and children.