A few days ago, Hazem left his wife and 11-month-old son in England and flew to Turkey with another Syrian-born doctor from Manchester to offer help on the front line in Aleppo.
The struggle to topple President Bashar al-Assad's regime has united Syrians far beyond national borders and while some have chosen to take up arms, Hazem and Ammar came with a shipment of first aid kits.
After barely a week attached to the Free Syrian Army units fighting Assad loyalist forces in the northern city of Aleppo's Saif al-Dawla area, the pair have performed life-saving procedures and experienced life-changing moments.
"Sometimes it's just a diagnosis or organising the work that can make a difference," said Hazem, a trained doctor who has emergency experience from Manchester, after helping treat a young fighter with a bullet wound to the leg.
He is working from a mosque basement in Saif al-Dawla that has been turned into a makeshift clinic since clashes intensified there earlier this month.
When the fighting for control of Aleppo began last month, in what the regime itself vowed would be "the mother of all battles", much of the medical staff in Syria's second city fled to safer areas or left the country altogether.
Hazem's and Ammar's project matured two months ago.
"We knew medical practitioners had left and we could see on videos posted on YouTube that sometimes first aid was not given properly," he explained.
"So we designed a very simple course for people with no medical background on how to deal with gunshot wounds, bleeding, fractures," he said.
They also prepared first aid kits for members of the Free Syrian Army heading to the front line. The bags include essentials such as sterile dressing, trauma fix and splints.
"We have already distributed 500 bags," first in rebel-controlled zones west of Aleppo and then inside the besieged city itself, he said.
In a few days, Hazem and Ammar have already seen their share of violence and blood and developed strong friendships. But there was nothing they could do for Abu Azzam, the young unit commander who first welcomed them.
When his body was brought to the clinic, his face charred beyond recognition by a tank shell that struck him before he could fire his RPG, the doctors could not hold back their tears.
"As Syrians from the outside, we didn't see the full picture, how Syrians were really living, how Assad was eating their food and drinking their water," Ammar said.
"I have seen how big the atrocity really is... We will need at least 15 years to recover from this and for children the trauma will last longer," he said.
"But most of all, it's the young men and women I've met here, they are fantastic and so generous. They feed you before touching their own food," the 41-year-old father of two said, his voiced choked with emotion.
"They have tasted freedom and they are so determined now. Nothing will stop them. It has made me so proud to be Syrian. It has changed me so much."
Asma, a 25-year-old Kuwaiti-born Syrian who has already served several months on the front line, sat on a plastic chair in the middle of the mosque-cum-clinic stroking the rim of her cup of tea.
Wearing a bright white nurse's blouse and white headscarf, she exuded a sense of inner calm despite the din of a war-time clinic that echoed around her.
"I came for the first time in 2011 and came back in May. My honour was at stake. I had to. Syria for me had become like a mother who needed a daughter," she said.
Already a keen cyber-activist before she came to Syria, she took part in several demonstrations and then decided to take first aid courses to make herself useful closer to the action.
She spent days in the heart of the Salaheddin district with several other girls her age to volunteer in a similar clinic before the army muscled in and forced everybody to relocate to neighbouring Saif al-Dawla.
"I always used to be scared of injections and couldn't bear the sight of blood. Now I can see everything," she said.
"Those nights under the shelling, sometimes in complete darkness... I felt a deep connection with the people. I know what it is to be Syrian now," Asma said.
"I will never go back to Kuwait. I have come home for the last time."
Explore further: Signs Syria may be lifting Facebook, YouTube ban