Nannie Doss may have seemed like “a loving grandmother with a charming smile,” as one local Oklahoma newspaper described her. But investigators began to suspect there was something sinister behind that smile after every member of her family mysteriously died, one by one, over the years.

In the end, the “Giggling Granny” admitted to murdering 11 of her family members.

The sensational case made headlines across the country at the time, and it has recently sparked newfound attention on social media. PEOPLE is looking back at Doss’ crimes and how authorities in Oklahoma finally came to realize she was responsible for her family members’ deaths.

Doss’ Childhood Traumas

Doss’ childhood was heavily impacted by her “abusive and demanding” father, Jim Hazle, according to the Encyclopedia of Alabama. Born in 1905 in Calhoun County, Ala., Doss was said to have “had an unhappy and difficult childhood,” as her father largely kept her out of school to work on the family’s farm. He “forbade his daughters from wearing makeup or dress clothes” growing up.

Doss’s father kept her and her three sisters from attending social events, as well, according to The Muskogee Phoenix. According to the newspaper, this strict shielding and a head injury Doss sustained — when, aboard a train, her head was slammed into a metal bar — contributed to her struggles growing up. The injury led to “severe headaches,” according to the newspaper. Yahoo! wrote that the head injury had also “impacted her view of life as a whole.”

Nannie Doss (right)

A Life of Murder

Doss had five husbands throughout her life, first marrying at the encouragement of her father when she was 16 years old, according to the Phoenix. She and her first husband, Charley Braggs, had four daughters between 1923 to 27 while living with his mother, according to the newspaper, leading to Doss’ becoming increasingly stressed. Two of her daughters suddenly died in 1927 from suspected food poisoning, prompting Braggs to become suspicious and leave his wife, taking his oldest daughter Melvina with him, according to the Phoenix. 

Braggs’ mother then suddenly died, and he returned to his childhood home soon after he and Doss divorced. According to the Phoenix, he is the one surviving husband throughout Doss’ life.

The newspaper reported that Doss went on to marry four more men – Frank Harrelson, an “alcoholic” who died after ingesting rat poison 16 years into their marriage; Artie Lanning, “an alcoholic womanizer” who also died after ingesting rat poison soon before Doss allegedly burnt down their house with his mother inside; Richard Morton, who died three months into their marriage after drinking coffee spiked with arsenic, and Samuel Doss, a “Nazarene minister who disapproved of [Doss’] romance novels” and died a little more than a year into their marriage from a similar arsenic poison found in his coffee.

Doss’ final husband’s death raised suspicion, according to the Phoenix, leading to a local doctor performing an autopsy that revealed the “massive” amount of arsenic in his system.

Doss Confesses to the Killings

Samuel Doss’ 1954 murder, which led to Doss’ arrest, was the last in what is suspected to be a 27-year killing spree that took at least 11 members of her family’s lives. In addition to her husbands, Doss is believed to be responsible for the deaths of two of her children, her own mother, Lanning’s mother — who was her mother-in-law — one of her own sisters and two of her grandsons.

She confessed to the crimes while being questioned for Samuel’s murder, according to the Encyclopedia of Alabama, leading to an initial death sentence after she was found guilty for murder, according to the Alabama Encyclopedia. A judge later declared her insane, however, which removed her death sentence.

Doss died in custody at the McAlester state prison in Tulsa, Okla., after she was diagnosed with leukemia, according to the Phoenix. She was 59 years old, and according to the newspaper, died exactly 10 years after she was first taken into custody.