Human rights activist and senior Pakistani lawyer Asma Jahangir died in Lahore on Sunday due to a cardiac arrest, The Express Tribune reported. She was 66. Some reports said the lawyer has been battling cancer for years now.

Jahangir, born in Lahore in January 1952, was the first woman to serve as the president of Pakistan’s Supreme Court Bar Association. She was also the United Nations Rapporteur for Human Rights, and a former Pakistan Human Rights Commission chief.

Jahangir was well-known for speaking up against human rights violations and was a staunch supporter of democracy. She was an outspoken critic of the military’s interference in civilian rule and a defender of the rule of law. Jahangir had written for many publications, and authored two books.

Soon after reports of her death emerged, many users took to Twitter to express their condolences.