Two separate groups of men suspected to be ISIS fighters were found slaughtered near Mosul, Iraq.
In the first case, the bodies of 15 suspected members of ISIS were found bound and blindfolded on the side of a road in Mosul.
Human Rights Watch has said that it's likely they were shot by a group affiliated with the Iraqi regime, which has hunted down thousands of suspected ISIS members while trying to clear them from the region, according to the Daily Mail.
At least one of the men, 31-year-old Qusay Mohammed, was on a government list of 90,000 men wanted in Iraq, which includes those suspected of being part of the terrorist group.
"It is hard to come to any conclusion other than that they were in the custody of government forces when executed," said Human Rights Watch researcher Belkis Wille.
Two of the men had been taken into a field, where one of them was made to kneel as he was shot from behind.
Another group of 11 suspected ISIS members was found dead 20 miles outside of Mosul, this time suspected to have been killed by a group of vigilantes seeking revenge on the jihadists. The men in this attack were also blindfolded and hand their hands bound.
Others said the men were innocent, and had been victims of an angry mob, The Telegraph reports.
The group, called Hammam al-Alil revolution, has said on its Facebook page that it is hunting down and killing members of ISIS. The vigilante group reportedly formed about six months after Hammam al-Alil, a town in Iraq, was taken back from the terror group.
"Soon we will start out operation, we are now locating Daesh families," read the group's first post from May 28, using an Arab word for ISIS. "We will make them regret joining. Good luck everyone."
The group, which has told its members to "burn them and their families," has posted the addresses of dead or captured ISIS fighters, instructing members to target their families.
"It's a reciprocity," said a member identified only as Omar, whose cousin was killed by ISIS. "They hurt my family, now we will hurt theirs."
Ali Hamed Ahmed, 65, said that his family was in danger, because three of his sons had joined the terrorist group.
"Our family is being punished for the sins of our sons," said Ahmed. "We have great shame for what they did, but they are not here now and this is our house. This is not right."
ISIS militants continue to terrorize the region. On May 26, the group is reported to have killed 27 people, including women and children who were attempting to flee, according to Haaretz.
"Shooting children as they try to run to safety with their families -- there are no words of condemnation strong enough for such despicable acts," said U.N. High Commissioner for Human Rights Zeid Ra'ad Al Hussein.