Ansis Alberts Kaupēns was born on November 2, 1895, in Platone Parish, Latvia. Baptized into the Lutheran faith, his early life was relatively obscure. His background was unremarkable in many ways, and little is known about his family or education.

In 1916, during the First World War, Kaupēns was conscripted into the Imperial Russian Army, where he began his formal military training. After the Russian Revolution, he transferred into the Red Army, specifically the 9th Latvian Riflemen Regiment, serving with the rank of sergeant. By 1919 or 1920, Kaupēns deserted the army and returned to Latvia, slipping into civilian life under a new identity. He took up work as a paper hanger in Jelgava by day.

Ansis Alberts Kaupēns committed a series of serious crimes in Latvia from 1920 to 1926. He started his criminal activities by committing his first robbery on January 29, 1920. Over the next six years, he engaged in more than 30 robberies. During this time, he was also responsible for 19 murders.

Kaupēns targeted various locations, including highways, in his robberies. One notable crime occurred on September 27, 1923, when he stopped and robbed a passenger train between Viesīte and Daudzeva. While Kaupēns worked as a paper hanger during the day, he continued his criminal actions at night.

Most of his robberies involved ambushing lone travelers or small groups on foot or horseback. He used a firearm in almost all his crimes and was known to kill victims who resisted or simply stood in the way.

His final confirmed robbery took place on May 29, 1926, just days before he was captured. Authorities had been closing in on him for some time, and on June 8, 1926, he was finally arrested. Following his arrest, he was tried and later sentenced to death. Kaupēns was executed by hanging on May 6, 1927. After his execution, he was buried in Svēte Parish.