After Hamza died, Ahmed took the stone out of one of the few olives he was given for lunch by the prison guard and used it to scribble on the wall.
"In memory of a father of three girls, who passed away in this cell. He wanted to live."
Ahmed had known Hamza for only a few minutes, but, he says, he will find him impossible to forget.
That morning, Ahmed had just been thrown into solitary confinement upon arrival at the government's political security branch in Damascus.
Ahmed knew it was wise to keep quiet when arriving at a new detention facility. He had been passed on for questioning to other branches of the regime's general security directorate since his arrest and received the same "welcoming party," as he calls it, everywhere.
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"The first two days they beat you and torture to break you up," he said. But the new cell had only walls and no loo and he had to go.
"I was stupid," he said. "I knocked on the door and asked to go to the bathroom.
"The guard said, 'Yes, we will take you'. Once out in the corridor, they started beating the hell out of me and told me to do it there.
"I wasn't able and they threw me back in solitary," he recalled, smoking a cigarette nervously.
"They threw him in my cell. He was red from blood and was wearing only boxer shorts and a T-shirt that was torn apart.
"'He told me he was cold. I put his head on my leg, gave him my shirt and we started talking."
Hamza was a car dealer from Old Damascus. He had been detained over his alleged involvement in the revolution. "He fought for the right to a better life," Ahmed said.
Hamza told him of his three daughters. "I still remember the names: Sarah, Fayruz and Afaf," Ahmed said. Then he grabbed the long beard Ahmed had grown in detention and begged him to contact his family if he ever made it out.
"He closed his eyes," Ahmed said. "I thought he was sleeping as his hand was still holding my beard; then, suddenly, it dropped."
"I was shocked, I was crying," he said as his eyes reddened and teared up and he lit another cigarette.
"I told the guard he had died. He laughed. 'And what should we do?' he said."
Hamza's body was left in Ahmed's cell for two days. Then the guards told Ahmed to take the body out of the cell.
"There was a line of them outside, waiting. They began to hit me as I carried him."
Ahmed hunched his head down, drawing his face close to Hamza's body. "Unfortunately, he smelt," Ahmed said. He let the body go onto the ground and rushed back to his cell. The guards followed.
"One said, 'For being a strong man, I'll give you a present,' and he tasered me on the back," Ahmed said.
"I didn't feel anything. No pain; the pain was inside, I had lost the feeling of physical pain."
There was no other reason why Hamza was thrown in his cell, other than the guards' sadistic pleasure based on their disdain for human life, Ahmed said.
It was the spring of 2012 and Syria was descending into violence that continues today.
According to the Syrian Observatory for Human Rights (SOHR) in the first four-and-a-half months of 2014, 847 prisoners, including 15 minors and six women, have died of torture, summary execution and maltreatment in Syrian jails and military bases.
Since the beginning of the conflict, some 18,000 people held by the government have disappeared, and many are feared dead, SOHR said.
Ahmed went through it but survived. IBTimes UK met him at a café near Taksim Square, in Istanbul, where he now lives as a refugee.
As a Homs native, he was double-crossed by a fellow activist and arrested in early 2012. He was not a rebel fighter but had actively supported the uprising against the government of Bashar al-Assad, working on logistics and hunting for medical supplies, food and money.
He said the hardest days of the detention were the first seven days when "no one talks to you, they only beat you."
In the hands of the Assad's security services, he was tortured at length. He was hanged naked for hours, showered with water and then electrocuted several times. His nails were torn from his left foot and his right calf was skewered.
Now he laughs as he shows his gnarled nails' regrowth: "This is nothing compared to what other people went through," he said.
He sports a long scar on his forehead and said a dentist asked him for about $3,000 to fix what was left of his jaws and teeth. His vision sometimes gets blurry, and sudden headaches are a daily companion, he said.
After five months in Damascus, a judge transferred him back to Homs where he faced trial on charges of belonging to a terrorist group.
As an educated son from a wealthy family, he was luckier than many others. His mother had lost her husband and was willing to go to extreme lengths to bring her only son back.
When she heard he was about to be moved to a military jail, she gathered her savings, got in touch with the right people in the administration, paid a bribe of 8 million Syrian pounds (£30,000) and secured Ahmed's release.
"My mum is a hero," he said. "She went to the most dangerous places to have me freed."
He was released on his 31st birthday, in October 2013. A week later, a military vehicle pulled in front of his home.
His mother told him not to worry: They had paid and he was a free man now; but Ahmed was so traumatized by his experience that his body shook at the sight of a uniform. He hid in the basement. It was the right thing to do.
"They wanted to bring me back," he said. "Someone had given my name to the air force security in Homs. She told them I was in Damascus and they believed her."
Ahmed was left with two options, joining a rebel group or flee. He chose the latter.
"When I entered jail I knew everyone involved [in the uprising] in Homs," he said. "When I came out it was different. Things had changed."
More important, he wanted to help his mother and find a job to to repay her.
He paid a smuggler who had robbed him before to lead him across the Lebanese border. "He said, 'give me all you have, or I hand you in to the military,'" Ahmed said.
From Lebanon he made his way to Turkey and then Istanbul.
As we talked, rebels were completing their withdrawal from Homs, marking the end of three years of resistance.
Ahmed is disheartened but not resigned. "Everything we tried to build is cracking ... but it doesn't mean we cannot build it again," he said, vowing to go back one day.
"I love my country, but mainly I love my city a lot, I love Homs.
"When I was at school I use to carve or scribble my name around the city. I never thought I would have done it inside the prisons' walls as well, but now it's there. I'm everywhere there."
Ahmed's attempts to contact Hamza's family have so far been unsuccessful.
Names have been changed to protect their identities.