The last message ever sent by Nika Shakarami, 16, was to a friend saying she was running from armed security forces.
Like tens of thousands of other Iranians, she had taken to the streets of Tehran to denounce the government following the death of a young Iranian Kurdish woman in police custody last month.
After her message on September 20, she was missing for 10 days.
Her family searched police stations and hospitals. They finally found her in a morgue at a police detention centre in the capital.
“When we went to identify her, they didn't allow us to see her body, only her face for a few seconds,” Atash Shakarami, Nika's aunt, told BBC Persian.
It was only when authorities released the body to the family for burial that they saw the extent of Nika's injuries.
“In the morning, when [the police] went to hand over the body, they saw that her nose was destroyed and her skull was broken and disintegrated from multiple blows of a hard object,” Atash Shakarami said, according to The Telegraph newspaper.
She added that the family were told Nika had been held by Iran's Islamic Revolutionary Guard Corps and briefly detained in Tehran's notorious Evin Prison.
Her family say they took her to their home town of Khorramabad for burial on Sunday — which would have been her 17th birthday — but security forces “stole” Nika’s body.
They say they had assured authorities they wouldn’t hold a funeral but one source told the BBC that authorities then buried her body in Veysian, around 40km away.
Anti-Iran regime groups reported that a protest that marched on the graveyard where Nika’s body was buried by authorities saw people chanting “death to the dictator” before security forces attempted to disperse crowds with teargas and live ammunition.
Atash Shakarami, who has posted about Nika’s death on social media, was also arrested on Sunday, the BBC said.
Dozens have been killed by authorities since street protests erupted after the death of Mahsa Amini on September 16 after she was detained by morality police in Tehran for allegedly failing to observe the Islamic republic's strict dress code for women. Thousands have been arrested.
At rallies in Iran women have removed their headscarves and many have cut their hair in protest to the government’s treatment of women.
At solidarity protests around the world, women have also cut their hair as governments condemn the crackdown by authorities.
The United States will impose “further costs” on Iran for its lethal crackdown, President Joe Biden said on Tuesday, drawing accusations of “hypocrisy” from Tehran.
Rights groups voiced deep concern after Iranian riot police used teargas and paintball guns against hundreds of students at Tehran's Sharif University of Technology on Sunday night, with video footage showing detainees being taken away with hoods over their heads.
Protests also spread to schools, with video footage shared by Kurdish rights group Hengaw showing schoolgirls demonstrating in two cities in Amini's native Kurdistan province.
“Women, Life, Freedom,” the young female protesters chanted as they marched down the central strip of a busy motorway in Marivan in footage seen by AFP news agency.
In his first public comments on Amini's death, Iran's supreme leader Ayatollah Ali Khamenei, 83, stressed on Monday that Iranian police must “stand up to criminals”.
Rights groups warned that this would be seen by police as protection for abusing and killing protesters.
At least 92 protesters have been killed so far in the Mahsa Amini rallies, said Oslo-based group Iran Human Rights, which has been working to assess the death toll despite internet outages and blocks on WhatsApp, Instagram and other online services.
Amnesty International said earlier it had confirmed 53 deaths, after Iran's semi-official Fars news agency said last week that “around 60" people had died.
At least 12 members of the security forces have been reported killed since September 16.