The 28-year-old was one of at least 150 soldiers and family members who had been trapped in Jisr al-Shughur hospital for almost a month.
As Syria's Al-Qaeda affiliate Al-Nusra Front and other Islamist factions overran the facility last week under heavy shelling, some soldiers managed a harrowing escape to a government-controlled area a few kilometres (miles) away.
From a hospital bed in Syria's coastal city of Latakia, the muscular and bearded Assaf told AFP that before he could reach safety, shrapnel struck his right ankle and bullets pierced his stomach.
"I felt like I was about to faint just as armed men started coming towards me. It looked like they were going to shoot me, but they left me after they thought I was dead and took my phone, wallet and weapons," he said.
Al-Nusra and its allies took full control of the hospital complex on Friday, after seizing the town of Jisr al-Shughur on April 25.
But official Syrian state media said the army had successfully "broken the siege" on the hospital.
Head of the Syrian Observatory for Human Rights Rami Abdel Rahman said more than 90 regime forces were able to reach safety, while others were killed trying to flee the hospital.
- Reaching safety -
According to Assaf, government soldiers were given an order to withdraw.
"We were in touch with the leadership, and we were told that an explosion" would be detonated by rebels "digging a tunnel under the hospital."
"We received an order to leave the hospital before 8 am, which is when the explosion would take place," Assaf said.
The soldiers formed small groups.
The first group formed an advance party to cover those escaping, while the second contingent carried out the wounded.
A third group, Assaf said, was in charge of "evacuating the civilians," and the fourth "provided covering fire from behind."
After being wounded during his escape, Assaf waited until nightfall to resume his trek towards government-held territory.
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It was midnight by the time he reached safety.
"We walked between trees and bushes. We didn't know how much time had passed until we arrived the next day at a military position," said another wounded soldier, Nawwar Bader Saleh, 25.
"After I was hit in my left leg, I finished the rest of the journey by crawling and walking."
- 'Burst into tears' -
According to the Observatory, regime soldiers were running out of food and rations in the hospital, and by last week wanted out "at any price."
Assaf said the besieged soldiers all felt that "being killed outside the hospital would be better than being inside when it exploded."
Earlier this month, President Bashar al-Assad had pledged not to abandon the soldiers, who have been hailed in regime-controlled areas as heroes following their escape.
While dozens escaped, others were killed in the fierce fighting around the hospital complex as army units backed up their trapped comrades.
Rabih al-Asmar, another soldier receiving treatment in Latakia, said the rebels "didn't differentiate between combatants and civilians."
"They shot at us as we were escaping, and a number of people died," he said.
Mohammad Zahran, 29, described his days in Jisr al-Shughur hospital as "a nightmare".
Still recovering from wounds in the chest, Zahran's account was marked by long pauses as he regained his breath.
"I used first aid kits to partially stop the bleeding. When I met up with the other units, they helped me get here in an ambulance, and I burst into tears."
Mohammad Mohammad, a fellow escapee, said his family was overjoyed when he finally escaped.
"Whenever I talked with my mother from inside the hospital, I would tell her that I thought I could die at any time," he said.
"When I left and called her, she was full of joy."