Iranian security forces killed a teenage boy by firing a shotgun at him at point-blank range in the city of Mashhad.
Abolfazl Adinezadeh, 17, skipped school to join anti-government protests on 8 October, but he never returned home.
Authorities have not commented. But his death certificate said he died as a result of liver and kidney damage caused by birdshot.
The sources cited a doctor as saying it was fired less than 1m (3ft) away.
“What crime had he committed, that you sprayed his stomach with 24 birdshot?” Abolfazl’s father pleaded at his funeral, a video showed.
Abolfazl’s parents initially had no idea what had happened to him after he took part in the protests, according to the sources.
It was not until the next day that the education ministry telephoned and told them to pick him up from the local police station.
But when they got there, they were told that he was dead.
Abolfazl’s grave is decorated with photographs of the teenager as well as food and flowers
“You zip your mouth and do not talk to media,” Abolfazl’s father was warned at the police station, the sources told the media.
The sources said the family was put under pressure to say that their son was a member of the Basij, a notorious paramilitary force that is involved in the violent crackdown on the protests.
Authorities have accused “rioters” backed by Iran’s foreign enemies of killing Basij members and other security forces during the current unrest.
Plainclothes security personnel were also present during Abolfazl’s funeral, shushing mourners who wanted to express their anger, according to the sources.
Abolfazl’s aunt held up a picture of him over his grave, but a female agent snatched the frame and put it under her veil, they said.
Some mourners were also stopped after the funeral and asked to delete the videos from their mobile phones.