Jeong Cha-sun, the mother of student activist Park Jong-chul, whose death by torture sparked a nationwide pro-democracy movement in 1987, passed away at the age of 91 on Wednesday.

The bereaved families of Jeong said she died at around 5:20 a.m. at a hospital in Gangdong-gu, eastern Seoul. Park Jong-bu, Jeong's oldest son, told local media outlets that she "passed away peacefully with a smile on her face."

"I think it was because she thought she was going to be with her son," he said, referring to his younger brother, who is one of the most important figures in South Korea's pro-democracy battles against the dictatorial regime of the 1980s.

After a military coup in 1979, Army Gen. Chun Doo-hwan rose to power and became the official president of South Korea in 1980. He stayed in power throughout most of the decade, and the strongman's repression of his political rivals made it nearly impossible for him to be replaced as the country's leader.

Authorities cracked down on protests across the country, including ones led by the students of Seoul National University. Park Jong-chul was one of those students.

On Jan. 13, 1987, Park was taken in for questioning by police for his suspected involvement in the protests and was tortured to his eventual death a day later. In a bid to cover up the brutal torture, the police falsely claimed that he died of shock.

The infamous excuse given during a press conference following his death was that the investigators "slammed the desk with a thump, and Park went ‘Uh!’ and died."

Park's death sparked nationwide unrest that ultimately led to civic protests in June of that year, which pressured Chun to submit to the public's demand and adopt a direct presidential election system.

Director Jang Joon-hwan’s 2017 film, “1987: When the Day Comes,” tells the story of the series of events leading up to the June protest, which begins with Park's torture and death. Actor Yeo Jin-goo plays Park in the film.

Park's parents had contributed to the pro-democracy movement following their son's death. Park's father, Park Jeong-gi, passed away in 2018 at the age of 89.

Jeong is survived by her son Jong-bu and her daughter Eun-suk. Her funeral is being held at the funeral parlor of the Kangdong Sacred Heart Hospital in Gangdong-gu, Seoul.