Wisam, who arrived in Istanbul about a year ago after fleeing Syria, went missing on July 23 and was found two days later in the city's Yenikapi district.
He previously had been threatened, kidnapped and raped, according to Kaos Gay and Lesbian Cultural Research and Solidarity Association (KAOS GL), a Turkey-based rights group. CNN is not using the victim's last name out of concern for his family's safety.
"We identified him from his pants... They had cut (him) so violently. So violent that two knives had broken inside him. They had beheaded him. His upper body was beyond recognition," said one friend, whom CNN is not naming for safety reasons.
"If you saw his body, if you even saw a picture of it, you would faint," said another friend, who asked CNN to identify him as Mohammed out of fear for his safety. "It was as if he was attacked by a beast."
Wisam had been stabbed 20 times, his organs were removed and he had been beheaded, according to Alex Benjamin, who works for an organization that aims to help LGBT refugees get expedited asylum.
"Police are doing nothing," Benjamin said, "because he is Syrian and because he is gay."
Police told CNN they were not authorized to comment on the case. Authorities haven't said whether Wisam was killed for being gay. As of Friday, his killers had not been detained.
Friend says he tried to get help, was turned away
Mohammed told CNN he tried to report his friend's disappearance, but was turned away by the Association for Solidarity with Asylum-Seekers and Migrants, an organization that assists refugees.
Gizem Demirci Al Kadah, a representative in Istanbul for the organization, declined to comment on the case.
"Yes, there are cases that we cannot help. But we cannot comment on this," he said. "But we do try to do everything we can to help those who come to us."
Going to security forces to report Wisam's disappearance wasn't an option, Mohammed said, because he didn't have papers. Like many refugees, Mohammed fled Syria without ID and hasn't been able to get a new one in Turkey.
'I am so scared'
According to KAOS GL, the attack has left the man's friends afraid to go outside.
After fleeing violence in Syria, now they say they fear for their safety in Turkey.
"I am so scared. I feel like everyone is starting at me on the street...No one cares about us. They just talk. I get threats over the phone. ... If you are gay, you are everyone's target," one of his roommates told the organization.
Gay rights activists in Turkey have said gays are facing increasing threats there.
And many LGBT refugees from Syria have said they feel they have to hide who they are in Turkey. They feel vulnerable to attack from Syrians who view homosexuality as a sin, and unsafe in a nation that they say doesn't protect them or its own LGBT community.
A gay couple who spoke to CNN last year from Turkey said they fled Syria after someone tried to run them over with a car, and remained afraid their relationship would cost them their lives.
In June, a gay pride parade in Istanbul was interrupted by police with pepper spray and rubber pellets after 13 years of being allowed to march uninterrupted.
At the time, activists told CNN it was an attempt by President Recep Tayyip Erdogan to appeal to his conservative base.
Mohammed told CNN the killing also highlights the difficulties refugees face in Turkey. Many who arrive aren't able to get identification documents, find work or make ends meet while they wait months or even years for their asylum applications to go through.
"Someone needs to do something to protect the rest of us, not just LGBT," he said. "But handle all of these other problems we face living here as refugees, gay or not."