In front of 300 villagers, Halima's father shot her in the head, stomach and waist -- a public execution overseen by local religious leaders in Afghanistan to punish her for an alleged affair, AFP reports.
Halima, aged between 18 and 20 and a mother of two children, was killed for bringing "dishonour" on her family in a case that underlines how the country is still struggling to protect women more than 11 years after the fall of Taliban regime.
Police in the northwestern province of Badghis said Halima was accused of running away with a male cousin while her husband was in Iran, and her father sought advice from Taliban-backed clerics on how to punish her.
"People in the mosque and village started taunting him about her escape with the cousin," Badghis provincial police chief Sharafuddin Sharaf told AFP.
"A local cleric who runs a madrassa told him that she must be punished with death, and the mullahs said she should be executed in public.
"The father killed his daughter with three shots as instructed by religious elders and in front of villagers. We went there two days later but he and his entire family had fled."
Amnesty International said the killing, which occurred on April 22 in the village of Kookchaheel in Badghis province, was damning evidence of how little control Afghan police have over many areas of the country.
"Violence against women continues to be endemic in Afghanistan and those responsible very rarely face justice," Amnesty's Afghanistan researcher Horia Mosadiq said.
"Not only do women face violence at the hands of family members for reasons of preserving so-called 'honour', but frequently women face human rights abuses resulting from verdicts issued by traditional, informal justice systems."
Police in Baghdis, a remote and impoverished province that borders Turkmenistan, said Halima had run away with her cousin to a village 30 kilometres (20 miles) away.
Her father found her after 10 days and brought her back home, where clerics told him he must kill her in front of the villagers to assuage his family's humiliation.
A Badghis-based women's rights activist said he had seen video footage of Hamila's execution, which AFP was not able to obtain.
"On the video, she is shot three times in front of 300-400 people. Her brother witnesses her death and breaks down in tears," said the activist, who declined to be named to avoid reprisals.
"She is sitting on her knees in the dust, wearing a large chador veil. A mullah announces her funeral prayers first, then her father shoots her from behind with an AK-47 at a distance of about five metres.
"We have learned that a Taliban shadow governor in the region asked the mullahs to issue the death penalty for her.
"The local religious council first said she should be stoned to death, but since the cousin was not there, they decided that she should be shot."
It is not known what happened to the cousin with whom she ran away.
The activist added that Halima's husband had objected to the killing and tried to return from Iran before the execution.
Mirwais Mirzakwal, head of the Badghis provincial government's media department, confirmed the accounts of how Halima died but gave no further details.
Women in male-dominated Afghanistan still suffer horrendous abuse after the fall of the 1996-2001 Taliban regime, which banned them from attending school or any form of public activity.
Under the Taliban, women risked being beaten if they did not wear full burqas or if they left the house without a male escort.
In 2009, Afghanistan passed a benchmark law criminalising forced marriage, rape, beatings and other violence against women, but Amnesty and other campaigning groups say it is rarely enforced.
With international troops withdrawing next year, many Afghan women fear any advances made since 2001 will evaporate as the Taliban exert increasing influence at local and national levels.
Badghis police chief Sharaf said officers were investigating Halima's killing, but no one had yet been arrested.
"We are trying to bring the perpetrators to justice," he said, admitting that authorities had only limited power in villages such as Kookchaheel.
"It is a volatile place and on the border between Badghis and Herat province, and the Taliban is also active."