(CNN) Karam al Masri is watching his city die. Or more accurately, he is watching the life gradually ebb from it.
Masri is a 25-year-old photographer in Aleppo who documents the fatalism, fear and sometimes the defiance of tens of thousands of civilians who remain in rebel-held areas of the city now almost encircled by Syrian government forces and their allies.
Masri has witnessed and experienced enough tragedy to fill many lifetimes.
He has been detained by the regime's secret police and ISIS; he has seen others executed and expected to be killed himself. He has lost relatives and friends and watched his beloved city become a battlefield.
But he stayed on through the barrel bombs that rained down from helicopters of Bashar al-Assad's regime. He stayed on despite the snipers and the random shelling. And he continued taking photographs of the people, their spirit as well as their inconsolable sadness.
In broken Skype conversations across several days, Masri described how Aleppo's people are trying to continue their lives despite the bombardments. He says they have seen so much horror they are almost oblivious to it. Of course, the airstrikes are bad, he says, but in many ways the intense barrel-bombing of the past three years was worse -- more indiscriminate.
As if delivering good news, Masri says only half of the recent airstrikes have killed civilians.
Stallholders in the markets still offer their produce, though there is less of it and prices for many staples have doubled in a week. Children still go to school, though sometimes in makeshift underground classrooms. And the "White Helmets," the voluntary civil defense workers, race from one jumble of rubble to the next, though often only to retrieve the dead.
According to international aid organizations, more than 40,000 people have already left rebel-held parts of the city. Masri expects many more will finally give up and run the gauntlet if the siege of the city by Syrian forces and Iranian militia tightens. But many won't.
To leave a city before it is starved might seem an easy choice to an outsider. But many of those who could afford to leave have already gone. The tens of thousands left behind don't have the money to find a home somewhere else or have no family to help them.
They know the Turkish border is still closed and prefer to stay in their own homes rather than huddle in the mud and winter cold. And many of the younger men, Masri says, fear being conscripted into the army or militia if they leave. So they stay and wait.
Masri knows what it's like to be the target of the regime and its secret police.
Before the uprising began, he was a law student at the University of Aleppo. He was active on Facebook and called for a revolution in Syria like those that had toppled the Tunisian and Egyptian governments. One night in April 2011, there came the dreaded knock at the door. He was detained for a month and says he was beaten and tortured.
He was freed as part of a general amnesty but for six months kept a low profile, afraid of being arrested again. He dared not leave opposition-held areas of Aleppo to return to the university and finish his degree.
Eventually Masri picked up his camera again. He worked for the French news agency AFP (and still does), filing photographs and video of the bombings and life in Aleppo. But his job brought new dangers every day.
On November 28, 2013, a barrel bomb targeted the Myasar neighborhood.
Masri jumped in an ambulance with two friends, but they ran into an unexpected roadblock. Masked ISIS fighters stopped them, tied their hands and blindfolded them. Within hours, Masri and his friends were in a makeshift jail in an industrial area called Sheikh Najjar.
"They opened an iron door, they uncovered my head, and put me in an isolated cell as small as the one I was in when the regime arrested me," he recalls of that day.
Masri spent 45 days in an underground cell. His daily ration was half a slice of bread and three olives; some days there was no ration at all. He lost 20 kilograms (about 44 pounds) in weight and often felt like he would die from starvation. He was not tortured, he says, but believes that's because his captors intended to kill him. He was, after all, a cameraman; there were few worse sins.
Masri believes there were some 30 cells in that underground jail, holding men of the Free Syrian Army, activists and other journalists. As ISIS lost ground, the guards took their prisoners from one place to another, but every time they killed a few more of their hostages before herding the remainder onto buses. Masri saw the body of his friend Nour, the ambulance driver he had ridden with on that fateful day in November.
Some were released, but not Masri. He lost hope that he would ever get out.
"There were people captured after me and released and I was still a prisoner. I stopped counting the days," he says.
Then on May 2, 2014, Masri was freed unexpectedly along with a number of other men, apparently on the orders of a local ISIS leader, Abu Luqman.
As he re-entered Aleppo for the first time in five months, he could not believe his eyes.
"The city was unrecognizable, destroyed and empty," he recalls sadly.
His joy at being released was mercilessly cut short. While he had been in an ISIS dungeon, his family's apartment building had been hit by a barrel bomb. Unknown to Masri, his mother had been killed, along with several others in the building. His father, widowed and with no idea whether his son and only child was still alive, had left Aleppo and gone to Egypt.
When they spoke, his father begged Masri to leave the city. But he refused; even if it was unrecognizable, Aleppo held its spell over him.
Within weeks, he was holding his dying aunt in his arms, a woman he describes as his "second mother." Her body was lacerated by shrapnel after a barrel-bombing.
"I buried her with my own bare hands," he says, pausing as he remembers the day. "She did not have anyone, never married, no kids. This scene stays with me. I see it every time I close my eyes, every day."
A few months later, Masri was injured in his left leg by a sniper's bullet. He spent three months alone in a small apartment, no mother and no aunt to visit and care for him. The loneliness of that time still haunts him.
"I lost everything in this year. 2014 was horrible."
But when he recovered, Karam al Masri went back to roaming through rebel-held neighborhoods of Aleppo, taking his remarkable photographs.
"I focus on characters who survive the pain and endure and find strength to stay in spite of the horror of war," Masri said.
"I focus on the suffering of people and children, showing how they deal with this war, how they escape airstrikes and come out of destroyed buildings looking for their relatives."
"I also like to show stories that demonstrate how beautiful Aleppo is and how it used to be before the war. I dream that one day the war ends and I can take photos of beautiful Aleppo and not only images of destruction and devastation."
One of the characters he found -- and there is no shortage of them in Aleppo -- is 69-year old Abu Omar, who is a collector of vintage cars. His house was hit by a mortar and his wife and five children left the city. But he chose to stay, wiping the dust of war from his precious collection every day.
The rest of the time, Omar sits alone in an apartment, with an old record player for company. When one of his cars is damaged by mortar fire, it's as if one of his children has been hurt.
"Like me," says Masri, "Abu Omar can't give up on his city."
Another character he profiled is a 31-year old boxer, Shaaban Kattan, whose talent could easily have been a ticket to a different life. Instead, he began a club for youngsters to box and fans so they could escape the war, if only for a just a few short rounds.
"I liked this story because I was able to show how people are trying to forget the war, cope, endure and maintain some normalcy," says Masri.
Masri is methodical when he plans a story. He likes to take his time.
"I go and spend time with the people I am going to take photos of, I check the angles I want to take, I imagine the story in my head. It takes me sometimes a week to finish a story," he says.
The lens captures details, a moment perhaps, such as an image of a child who has lost his parents, that the naked eye cannot capture. That, to him, is the power of photography.
Masri does not pretend to be immune from his subjects.
"When I come home and look through the photos, then it hits me," he says. "I sometimes get really emotional and I wonder how I was not I affected by the horror my camera documented while I was taking pictures. I cry."
And there are times when his humanity and sorrow overcomes his profession. He recalls going to the scene of an airstrike.
"The entire family died except the father. The building was flattened, he was digging with his bare hands, digging and crying for two days. No help arrived. I did not take a single picture; I couldn't."
He recalls a barrel bombing in the neighborhood of Bab al Nayrab. An entire family emerged, covered in dust and crying.
"I was trying to comfort them, saying, 'Why are you crying? You are alive, thank God.' And they said they had lost their home, they had nothing, nowhere to go. They said they wished they died."
"I thought about them for a long time. How could we help them? Where did they go? It stayed with me."
Masri says that today, some people in Aleppo still urge resistance, futile though that might seem. There have even been small demonstrations urging the dozen or so fractious rebel groups to come together and form a "Jaysh Aleppo," or Aleppo Army.
Masri does not believe the regime and its allies will try to reduce eastern Aleppo to dust in street-to-street fighting. They don't need to; they can just stop food and diesel getting in, he says.
"There's not enough food stored for more than a month," Masri says. "If they force a siege for one month, people will die."
But he says he can't imagine leaving unless forced to by the Syrian army.
"I can't leave Aleppo. My family was buried here, I can't go away and leave their graves; it would be a betrayal. My mother could have left and saved herself, but she waited for me. She died waiting for me."
As he wanders among the ruins of his city, there's one place that Masri won't visit and never has since he was freed by ISIS: the apartment building where his mother was killed almost exactly two years ago.
From stalemate to slaughter: On the front lines of the battle for Aleppo