Lester Warfel Brockelhurst Jr. was born on January 4, 1914, in Peoria, Illinois. He was the first son of Lester Warfel Brockelhurst Sr. and Edyth DuPree, a couple who practiced the Mormon faith. Lester had a younger brother named Karl, born in 1930, and a sister named Fern Irene. When Lester was six months old, his family moved to Galesburg, Illinois. They lived there until 1926, when they relocated to Dallas, Texas.

In Dallas, Lester's father started an interior decorating business. Lester attended grade school in Texas before moving back to Illinois with his family. They settled in the village of Maquon, which is near Galesburg. Lester graduated from Maquon High School. After finishing school, he began working at his father's painting and decorating business, which had returned to Illinois from Texas.

During his time in Galesburg, Lester was involved in his church. He served as the president of the Young Men's Mutual Improvement Association and was also a Sunday school teacher. In high school, he participated in drama and public speaking activities. However, he could not join athletics due to a pole vaulting injury.

Lester met Bernice Felton when they both competed in a public speaking contest in Illinois. Over time, they developed a romantic relationship. Despite living 165 miles apart, Lester visited Bernice every two weeks and wrote letters to her during the intervals.

In January 1935, an argument about money with his father led to Lester leaving home. He hitchhiked to Chicago, where he attempted to rob a candy shop. He was arrested soon after and sentenced to two years in prison. Initially, he was sent to Joliet State Penitentiary but was later transferred to the Illinois State Reformatory in Pontiac.

Bernice kept in contact with Lester while he was in prison, and her father advocated for him. As a result, he was paroled after serving a little over a year. After his release, he moved in with Bernice's family and started working in a nearby department store and print shop. Lester wanted to take Bernice to get married in Salt Lake City’s Mormon Temple, but he lacked the financial means to do so. This frustration led to a life-changing decision for the couple. On March 31, 1937, Lester and Bernice began a crime spree across 18 states, motivated by robbery.

Lester Warfel Brockelhurst Jr. was involved in a series of violent crimes during a six-week crime spree across several states in 1937. On the same day that he and his girlfriend Bernice Felton disappeared, a local tailor named John Albin Theander went missing. Later, his body was discovered in Rockford, with a gunshot wound to the head. After this, Brockelhurst and Felton traveled to various locations, including Salt Lake City and Fort Worth. In Fort Worth, they held up a tavern. When the owner, Jack Griffith, tried to resist, Brockelhurst shot and killed him.

Their next major crime occurred in Little Rock, Arkansas. After leaving Theander's car behind, they walked to Memphis, where they were picked up by a wealthy landowner named Victor A. Gates. Upon arriving in Arkansas, Brockelhurst shot Gates in the head, robbed him, and disposed of his body in a ditch.

After these murders, Brockelhurst and Felton committed about 40 robberies and hold-ups, but no other murders were recorded during that time. They were ultimately apprehended on May 13, 1937, after a police officer noticed their car had no license plate and found a loaded gun inside. During questioning, Brockelhurst confessed to the murders of Theander, Griffith, and Gates.

Following their capture, Brockelhurst was taken to Poughkeepsie, New York, as authorities debated where to charge him. While in jail, he experienced fainting spells due to what officials deemed "overexcitement." Investigators looked into another unsolved murder of a gas station operator, Herman Luhrsen, which might also be linked to Brockelhurst's weapon.

Eventually, Brockelhurst was extradited to Arkansas, where charges against him were prepared. His trial began on June 14, 1937. Throughout the proceedings, both he and Felton were placed on suicide watch, as they had threatened to take their own lives if one of them did. Brockelhurst's defense team attempted to argue that he was insane, but a state mental assessment found him to be sane.

After deliberating, the jury convicted Brockelhurst of the murder of Victor Gates, sentencing him to death by electrocution. On March 18, 1938, he was executed. Before his execution, he made a final statement, expressing remorse for the situation and placing guilt on Felton as well.