In adulthood, Carl Panzram became a thief, stealing anything from bicycles to yachts, and was caught and imprisoned multiple times. While incarcerated, Panzram frequently got into trouble by attacking guards and refusing to follow their orders. The guards retaliated, subjecting him to beatings and other punishments. In 1907, at the age of 15, after getting drunk in a saloon in Montana, Panzram enlisted in the United States Army. Shortly thereafter, rebellious against any authority, he was convicted of larceny and served a prison sentence from 1908 to 1910 at Fort Leavenworth’s United States Disciplinary Barracks. Secretary of War (and future President) William Howard Taft approved the sentence. Panzram later claimed that any goodness left in him was smashed out during his Leavenworth imprisonment. In his autobiography, Panzram wrote that he was “rage personified” and that he would often rape men whom he had robbed, not necessarily because he was homosexual, but to dominate and humiliate them. He was noted for his great physical strength, which aided him in overpowering most men he encountered. He also engaged in vandalism and arson. By his own admission, one of the few times he did not engage in criminal activities was when he was employed as a strikebreaker against union employees. On one occasion, he tried to sign aboard as a ship’s steward on a U.S. Army transport vessel, but was discharged when he reported to work intoxicated.

Carl Panzram served time in prisons in Fresno, California; Rusk, Texas; The Dalles, Oregon; Harrison, Idaho; Butte City Montana; Montana State reform School, Miles City Montana; State Prison Montana {“Jeff Davis” #4194 and Jefferson Rhodes # 4396}; Oregon {“Jefferson Baldwin” #7390}; Bridgeport Connecticut {John O’Leary}; New York’s Sing Sing {“Jeff Baldwin” #75182}; Clinton Correctional Facility New York {“John O’Leary”}; Washington D.C. (#33379); and Leavenworth, Kansas {Carl Panzram #31614}. On June 1, 1915, Panzram burgled a house in Astoria, Oregon, but was arrested soon after while attempting to sell some of the stolen items. He was sentenced to seven years in prison, to be served at the Oregon State Penitentiary in Salem, where he arrived on June 24. On arrival, he became inmate number 7390 and was under the supervision of warden Harry Minto, who believed in harsh treatment of inmates, including beatings and isolation, among other disciplinary measures. Later, Panzram stated that he swore he “would never do that seven years and I defied the warden and all his officers to make me.” Carl Panzram helped fellow inmate Otto Hooker escape from the prison; while evading capture, Hooker killed Minto. The crime marked Panzram’s first known involvement in a murder, as an accessory before the fact. Panzram was disciplined several times while at Salem, including 61 days in solitary confinement, before escaping on September 18, 1917. After two shootouts he was recaptured and returned to the prison. On May 12, 1918, he escaped once again by sawing through the bars of his cell, and caught a freight train heading east. He began going by the name John O’Leary and shaved off his moustache. He would never return to the Northwest.

In August 1920, Carl Panzram burgled the New Haven, Connecticut home of Taft, whom he held responsible for his Leavenworth imprisonment. He stole a large amount of jewelry and bonds, as well as Taft’s Colt M1911 .45 caliber handgun. He then began a murder spree that spanned eight years and multiple countries. With the money stolen from Taft he bought a yacht, the Akiska. He lured sailors away from New York bars, got them drunk, raped and shot them with Taft’s pistol, and dumped their bodies near Execution Rocks Light in Long Island Sound. He claimed to have killed ten in all. The sailor murders ended only after the Akiska ran aground and sank near Atlantic City, New Jersey, his last two potential victims escaping to parts unknown. Panzram then caught a ship to Africa and landed in Luanda, Portuguese Angola. He later claimed that while there, he raped and killed an 11- or 12-year-old boy. In his confession to this murder, he wrote: “His brains were coming out of his ears when I left him and he will never be any deader.” He also claimed that he hired a rowing boat with six rowers, shot the rowers with a German Luger pistol and threw their bodies to the crocodiles.

After returning to the United States, he asserted that he raped and killed two small boys, beating one to death with a rock on July 18, 1922 in Salem, Massachusetts and strangling the other later that year near New Haven, Connecticut. On the Hudson River in June 1923 Panzram claimed that with a .38 pistol from a yacht he had stolen from the Police Chief of New Rochelle, New York that he shot a man for trying to rob him. After his last arrest in 1928, he claimed to have committed a murder while burglarizing homes between Baltimore and Washington, D.C. and two other murders of young boys in Philadelphia in 1923 and 1928. Carl Panzram later wrote that he had also contemplated mass killings and other acts of mayhem, such as poisoning a city’s water supply with arsenic, or scuttling a British warship in New York harbor to provoke a war between Britain and the United States. Carl Panzram was hanged on September 5, 1930. While the noose was being put around his neck, he allegedly spat in his executioner’s face and declared, “I wish the entire human race had one neck and I had my hands around it!” When asked by the executioner if he had any last words, Panzram barked, “Yes, hurry it up, you Hoosier bastard! I could kill a dozen men while you’re screwing around!” He was buried at the Leavenworth Penitentiary Cemetery.