The murder of Khurram Zaki by armed men in Karachi has underscored the vulnerability of activists and civil-liberties defenders in Pakistan.
Khurram Zaki, 40, was killed on Saturday in the southern Pakistani city by unknown assailants in an attack that also left a journalist dead and a bystander critically injured.
Zaki, whose funeral took place on Sunday, was known for his outspoken stance against the Lashkar-e-Jhangvi, a Sunni sectarian group; the Pakistani Taliban; and Abdul Aziz, a controversial religious leader.
In December 2015, Zaki led street protests demanding that Aziz be arrested and charged with hate speech for allegedly justifying attacks such as the Peshawar school massacre in 2014 in which at least 132 school children were killed.
A faction of the Pakistan Taliban, the Hakeemullah group, claimed responsibility for Zaki's killing, but the police were unable to verify those claims and said the group had previously taken responsibility for attacks it did not carry out in Karachi.
Speaking to Al Jazeera, Jibran Nasir, a Pakistani lawyer and activist, said he had no doubt why Zaki was targeted.
"The primary reason behind Zaki being shot dead was his constant activism in a bold manner," Nasir said.
"Zaki had an idea of what he was getting into. He received various threats. We've registered an FIR [First Information Report] in Karachi after his murder and given the names of people who should be held responsible. Aziz has been named as the prime suspect in the FIR."
The killing of Zaki, a former journalist and an active campaigner for human rights, comes at a time when Pakistani rights advocates feel they are increasingly under attack.
Saturday marked two years since Rashid Rahman, a human rights lawyer, was shot dead.
On April 24, Pakistan marked one year since Sabeen Mahmud, another prominent liberal activist, was murdered in Karachi.
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"Activists are vulnerable targets," Nasir said. "Terror outfits continue to spread a reign of terror by shooting them and achieving their purpose. But as activists, we knew what we were getting into and we signed up for this.
"We're talking about certain aspects of the law and core issues, and when you talk about this loudly, you make a lot of enemies. But we expected all this. It hasn't changed my life in any way and it didn't change Zaki's life either."
Mahmud was shot shortly after hosting a discussion on Balochistan's "disappeared people".
She was the director of The Second Floor (T2F), a cafe and arts space that has been a mainstay of Karachi's activists since it opened its doors in 2007.
Alleged culprit's confession
Mahmud had been present at the opening of the discussion in which Mama Qadeer, Farzana Majeed and Muhammad Ali Talpur - three prominent Baloch rights activists - had been speaking.
The alleged culprit, who also confessed to being involved in the killing of 45 members of the Shia Ismaili community in Karachi, told police that Mahmud had been targeted for her campaign against Aziz.
"We've pursued charges of different kinds against Aziz, including him having allegiance with ISIL [the Islamic State of Iraq and the Levant group, also known as ISIS] and him claiming a Shia lobby is working against him," Nasir, the Pakistani lawyer and activist, said.
"He knows who we are. I've seen videos of him naming me and Zaki. And a lot of social media campaigns have taken place against us, creating rumours and endangering our lives. I've suffered from that and Zaki suffered from that.
"But our actions and activism of the people landed him in hot water and we were able to break this insurmountable reign of terror that Aziz had over Islamabad."
It is widely believed that Aziz enjoys support in many parts of Pakistan, including that of his students at Jamia Hafsa, a madrassa in the heart of Pakistan's capital, Islamabad.
"What is the harm in trying the Islamic system?" Ayesha, a 26-year-old graduate of one of Aziz's seminaries, said to Al Jazeera earlier this year.
"The media raise all kinds of propaganda against us, but they never ask us for our or the maulana's [Aziz's] point of view."
Follow Faras Ghani on Twitter: @farasG
Source: Al Jazeera and agencies