An Iraqi policeman who refers to himself as "The Beheader" has boasted of the ease with which he has decapitated 50 Islamic State fighters and killed 130 in total.
Falah Aziz posts his gruesome work fighting Islamic State in the city of Mosul to his Facebook page while decked out in a designer black jacket.
Asked how it feels to cut someone's head off, he says: "Just that feeling, I can't explain how at ease I am with it."
"They've driven us to it. What they've done has killed our compassion. Finding your brother slaughtered, or your mother slaughtered.
"What they have done to us, we must do to them."
Aziz has been involved in the war for three years, having participated in the first Mosul battle in 2014.
He also smothers the ISIS terrorists while beating them but he stresses beheading is his speciality, Expressen reports.
"Every day, I swear, I slaughter them, as they've slaughtered us," he told the Swedish news site.
But an unidentified expert spoken to says his actions are quite clearly war crimes.
"It's quite clear these are vile war crimes," an expert told the outlet.
Other experts said there was a responsibility on Iraqi authorities and the international community to have the matter investigated.
One suggests all intelligence and support from the West should be withdrawn.
On his Facebook page, Aziz is holding up a bloody knife in his profile picture.
Other videos show him walking around, with Iraqi troops, carrying a severed head.
And beating blindfolded men who are sitting on the floor, with their hands tied behind their backs and hoods over their heads.
The prisoners are being beaten with whips and batons, and one of them is being suffocated by someone's hands over his mouth.
You do not see whether anyone dies, but Falah Aziz says: "Every day, I swear, I slaughter them, as they've slaughtered us."
In a video showing torture, men's voices bark orders at each other: "Hit him!
"Get the pillow."
Aziz looks like just another Iraqi police officer or soldier.
He walks around in military boots and wears the same brand of jacket worn by a lot of the troops, a black 5.11.
But he stresses that not everyone fighting ISIS does what he does: "No, no. Not everyone."
He says that beheading is his speciality.
None of the people he is fighting alongside can be seen protesting when Aziz cuts people's heads off.
They celebrate when he's chopped a head off.
Aziz yells : "The knife has done its work!"
His colleagues shout excitedly that: "Falah Aziz is cutting ISIS's head off."
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Several of the videos in Aziz's mobile phone clearly show his colleagues within the Iraqi Police Force, and Iraqi Armed Forces, not simply watching on in silence as he tortures prisoners and cuts their throats.
In one video, you can see a large group of soldiers parading down the street screaming, with Aziz leading the way and holding a severed head in one hand.
Another video shows a close up of Aziz cutting the head off a young man or boy, while surrounded by Iraqi troops.
In another video - which Aziz shared to demonstrate what he has done, but the image quality is too poor to determine whether he is involved - Iraqi troops can be seen beating men wearing civilian clothes and with their hands tied behind their backs, lying on the floor of a building.
The beatings are extremely brutal and radiate immense rage.
The men on the floor are being beaten with whips, something that looks like power cords and a metal object on a chain.
The men being beaten cannot protect themselves. They just scream.
The photos and videos Aziz has in his mobile phone and the material he has published on his Facebook page have changed over the years and changed with the war.
He shows off the videos as if they were normal.
His voice is indifferent and resolute: "My specific wish is that I slaughter them."
He has kept count of the people he has killed: "50 that I've cut the heads off. But 130 in total," he claims.
When asked whether the people whose heads he has cut off were dead or alive, he says: "No, no, alive."
And when specifically asked whether what appears to be a young man or boy being beheaded was alive or dead, Aziz says: "He's alive, him. We grabbed him in the toilets."
Public toilets have become a common hiding place during the war on ISIS.
It is usually the last place troops check, which is exactly why people have started hiding in them.
Aziz finds it easy to describe why he is doing this to the people who are captured.
"They've driven us to it," he said.
"What they've done has killed our compassion. Finding your brother slaughtered, or your mother slaughtered. What are you going to do? You don't know what you're going to do. What they have done to us, we must do to them."
By "them" he means ISIS. But the prisoners being tortured and killed are not getting a fair trial.
He describes how he has moved along the fronts during the Mosul battle.
Now he is fighting with the Iraqi Federal Police Force's 5th Division and refers to his commanding officers as "heroes Ali Alami and Abou Dergham".
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He explains that Iraq's most senior Shiite cleric, Grand Ayatolla Ali al-Sistani, called upon the people to fight against ISIS.
Ali al-Sistani issued a fatwa in which he urged the Iraqi people to declare jihad on ISIS, which resulted in 100,000 people joining the war – both civilians and people with paramilitary backgrounds from the many militias that existed in Iraq.
The majority of the Iraqi population are Shia Arab Muslims.
Under Saddam Hussein, Sunni Arabs were in power, but after the US invasion in 2003, all of Saddam Hussein's security forces, as well as his Ba'ath Party, were dismantled.
Since then, the governments have been Shia dominated.
In 2006-2007, there was a civil war in Iraq between Sunni and Shia groups, a war that began in the power vacuum after the US invasion, when a group of Sunni Arabs formed a resistance movement and Sunni extremists, al-Qaeda, established themselves in the country.
The Sunni uprising and al-Qaeda in Iraq were targeting Shia Arabs and Westerners.
Even Shia forces turned on the Western troops after the invasion.
Aziz feels that, among others, the Shia forces have done a lot for the war on ISIS – that they have been avenged and, by slaughtering ISIS, brought honour back to Iraq.
Now he is fighting in areas that are still under ISIS control in West Mosul.
A few weeks ago, he was shot in the thigh by an ISIS sniper.
He describes ISIS as mostly Sunni, a mix of Saddamites and terrorists, who joined forces and took control of Sunni areas in Iraq in order to proclaim a separatist state for Sunni Arabs.
It is an opinion he shares with a lot of Iraqi civilians as well as Iraqi generals – that ISIS is made up of former military from the Iraqi security forces dismantled by the US when Saddam Hussein was overthrown in 2003, of former al-Qaida in Iraq and of local mafia. Several of the people who joined ISIS have spent time in prison, among them the US-run Abu Ghraib prison in Iraq, which became notorious for torture and sexual humiliation.
Even ISIS's highest leader, Abu Bakr al-Baghdadi, spent time in Abu Ghraib before the US released him in 2010. ISIS illustrate the fact that Americans have been torturing Iraqis, by dressing their prisoners in the same orange overalls that the Americans have used in their prisons in Iraq and Guantánamo.
According to Falah Aziz, entire countries were involved in the emergence of ISIS:
"It's an Israeli plan, that they'd begun working together, Saddamites and terrorists."
The goal, he believes, it to destroy Iraq. "Destruction. It's an Israeli and American plan."
The fact that the US invaded Iraq in 2003, after having invaded Afghanistan in 2001, is usually explained by people who share Aziz's views as revenge for the 9/11 attacks.
In other words, the goal was not to protect the Iraqi people, but rather to overthrow Arab-Nationalist Saddam Hussein, who was considered a threat to the US and Israel, and seize control of the oil.
Another of the videos in Aziz's mobile phone shows him together with his colleagues from the Iraqi forces.
He is holding a knife. Both it and his hand are red.
"Here's the man who's slaughtering ISIS," cries one of the soldiers beside him.
Aziz looks into the camera: "This is your blood, you dogs."
A young man in the background praises him: "Well done!"
But in amongst his war photos are pictures that do not contain any violence. Four men feature regularly in his photos.
Their names are Ahmad Aziz, Ghazwan Aziz, Bashar Aziz and Waed Aziz. They are his brothers. Were his brothers. Older brothers.
"Now they're martyrs," he says.
"One of them was a teacher. What did he ever do to get slaughtered? He has five children."
Aziz finds it harder to talk.
"Four of my brothers died in my arms," he says.
"I'm the youngest. My brother said, 'Don't leave me.' I can't explain."
But he knows that it made him want to do the same thing in return.
"As they slaughtered my brothers, I slaughter them," he adds.
His mouth has responded to every single question in a clear and straightforward manner, but his eyes have said nothing. They express nothing.
The philosopher Friedrich Nietzsche once warned, "He who fights monsters should take care lest he becomes a monster himself.
"For if you gaze into the abyss long enough, the abyss will also gaze into you."
Aziz sees nothing but the abyss. He has climbed into it. And he has no plans to leave it.
The war has become part of him. Part of his skin, his thoughts, his soul.
He does not even think he will go on living.
An attitude he shares with many of the ISIS members he has fought against.
"I expect to die, not to remain here."