Investigators have found no match for casings of bullets that killed a prominent human rights activist, dashing hopes for quick answers to a murder that has raised fears for the safety of dissenting voices.
Gunmen on a motorcycle attacked activist Sabeen Mahmud late last Friday in Karachi, as she was leaving her cafe, where she held art exhibitions and talks.
Read: T2F director Sabeen Mahmud shot dead
She had just hosted a discussion on disappearances in Balochistan where the Pakistan Army is fighting insurgents.
Investigators recovered bullet casings from the scene but drew a blank.
"That suggests that a new group or new weapon has been used in the killing," a law enforcement official involved in the case, who declined to be identified because the topic is sensitive, said late on Monday.
Read: TTP deny involvement in Sabeen Mahmud’s murder
Police say their only witness is Mahmud's mother, who was with her and was wounded.
Investigators suspect the killers had a back-up team of two men on a motorcycle and police are poring over CCTV footage.
Desperate for clues, investigators are monitoring social media in hopes that loose talk could provide a lead, said another senior law enforcement official.
Authorities had earlier blocked the talk, titled "Unsilencing Balochistan", when it was scheduled at a different venue.
Read: Keep smiling, Sabeen
Mahmud had told friends that officials of the military's Inter-Services Intelligence agency visited her in 2013 to ask about her work and finances, the law enforcement official said.
She had recently asked friends if she should go ahead with the Balochistan talk, he added.
However, the army condemned Mahmud's killing, and went as far as to say its intelligence agents would help in the investigation.
Read: Intelligence agencies to assist in investigation of Sabeen Mahmud’s murder
Human rights workers have not been reassured.
"There's a lot of fear among the people, about whoever speaks out about Balochistan, what's going to happen," said Rukhsana Shama of the rights group Bedari.
"It's easy to point fingers at the agencies but no one knows."
For many Pakistanis, the insurgents in Balochistan pose a more alarming threat than militants.
Pakistan says the insurgent get help from neighbour and arch-rival India, but India denies this.
Security concerns in the province took on added urgency days before Mahmud was killed, when China's President Xi Jinping unveiled projects worth up to $46 billion for an economic corridor anchored there.
Read: Baloch ire prompts security fears for China-Pakistan Economic Corridor
The army has vowed to crush the insurgency.
The first law enforcement official said Mahmud's killers might have taken advantage of the tension between the authorities and Mahmud over her Balochistan activism.
"Our hunch is that some third party exploited the standoff," he said, suggesting India.
Read: Police files Sabeen Mahmud’s murder case under Terrorism Act
The case was unlikely to be solved if any security agency was behind it, the first official said.
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