What would prompt a group of Pakistani university students to turn on a classmate, strip him naked, and beat him to death on the grounds of their campus?
Investigators are still seeking answers to that very question, but Mashal Khan's outspoken views and social-media presence offer some possible clues.
The mob that lynched Khan on April 13 accused the 23-year-old of posting "blasphemous content" online, a crime that is punishable by death in Pakistan under colonial-era laws that have long been criticized by human rights groups. Blasphemy is a highly serious and sensitive charge, and even unproven allegations can lead to vigilante justice, including mob lynchings and violence.
Twenty-two people have been arrested so far over the killing, and police have said they have found no evidence to prove that Khan had committed blasphemy.
Khan, a journalism student at Abdul Wali Khan University in the northwestern city of Mardan, was an outspoken critic of conservative Islam and an apparent admirer of communist revolutionaries and controversial national figures.
The walls of his dorm room were adorned with posters of Karl Marx, Argentinian Marxist Che Guevara, and Baloch leader Nawab Akbar Khan Bugti, who was assassinated in 2006.
Those who met Khan describe him as a well-read and intelligent student who openly professed his Islamic faith. Yet he also questioned the role of religion in society, condemned sectarian violence, and was an open admirer of the region's pre-Islamic culture.
His outspokenness led RFE/RL's Radio Mashaal to invite him to participate in its Voice Of The Youth program just weeks before his death. In his March 24 appearance on the show, Khan was critical of Pakistan's political system and censorship in the country.
WATCH: Funeral For Student Lynched Over Blasphemy Allegation
Khan, who studied engineering for four years at the Moscow Business School in Russia, said he returned to his homeland to serve and enlighten his people.
"My mind opened after I started reading," said Khan, who was a fervent student of Western philosophy. "I began to understand the root of our problems in Pakistan."
Khan, who had traveled widely in Europe, was fiercely opposed to the feudal system still dominant in some areas of Pakistan. He was an advocate of social equality and was a self-confessed admirer of humanism, which places importance on the individual over the divine.
He also lamented peoples' lack of knowledge of the region's pre-Islamic history. "We have thousands of years of history. We were once worshipping fire," he said, referring to Zoroastrianism, a religion that was dominant in the region before the spread of Islam in the 7th century.
Attracting Threats And Abuse
Khan shared his views online, especially on Facebook, attracting abuse and threats from deeply conservative Muslims.
He posted photos of the founder of the Soviet Union, Vladimir Lenin, Chinese communist dictator Mao Zedong, and Abdul Ghaffar Khan, better known as Bacha Khan(Frontier Gandhi), who advocated for the rights of his fellow Pashtuns in the British Raj in the early 20th century.
Khan knew he had made enemies with teachers and other students for his secular views and for not following a religious code of life or attending Friday prayers.
Khan appeared to be aware that he could be accused of blasphemy, sharing a post in December 2016 that warned his followers that fake accounts had been created in his name.
"[They are] trying to blackmail me," he warned, adding that "someone is trying to taint my image."
The brutality of the attack shocked the Pakistani public and led to widespread condemnation, including from prominent Islamic clerics.
WATCH: Students Want 'Radical Elements' Expelled After Killing
Graphic video footage of the killing showed dozens of men outside the dorm kicking and hurling objects at a body sprawled on the ground.
Rights activists have held protests in several Pakistani cities to condemn the killing, and the United Nations has called the killing "unacceptable."
On April 18, Pakistan's parliament passed a resolution calling for the reform of blasphemy laws, the first time it has ever done so.
At least 65 people have been killed by vigilantes over blasphemy allegations since 1990.