Hassan is just 18 and a fighter with the Lebanese Shiite group Hezbollah, which threw nearly 2,000 men into the Syrian army's assault on the central town of Qusayr this week.
His father Ali was also among the ranks of the Hezbollah men battling rebels in the key town, many of them holed up in tunnels.
Hassan, a gunner, came back to his home in Baalbek in east Lebanon on Wednesday after three days of gruelling combat.
His father did not.
Hassan discovered that Ali had been killed on day one of the fierce firefights. Together they had left to fight in Qusayr, but now his 43-year-old father was dead -- shot twice in the chest.
"We were not in the same place, but I had a hunch, a weight on my chest. I was thinking of him all the time," Hassan admitted before breaking down in tears.
He quickly regained his composure: "I must be strong. From now on, I have to look after my mother and sister, then I will have to go back to the battle to finish what we started."
Hassan said the resistance put up by rebels in Qusayr had taken him and his comrades by surprise.
"On the first day, we advanced through the alleyways towards the centre of Qusayr, and then suddenly the rebels attacked us from behind," he told AFP.
"We could not see any fighters, we thought there was no one there," he added, still wearing his combat fatigues, a Hezbollah scarf draped over his shoulders and a weapon in his hand.
"When we had pushed through two thirds of the city, towards the north, they came out of tunnels and opened fire on us. We had a lot of fighters killed and wounded, all of them shot in the back," he said.
The regime assault on the rebel stronghold of Qusayr, in central Homs province, began on Sunday.
Troops backed by fighters from Hezbollah, a staunch ally of Syrian President Bashar al-Assad, stormed the town after seizing a string of nearby villages.
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Hezbollah forces were organised into 17 units of 100 men each, before storming the city from the east, south and west, a source close to the group said.
The town, which lies near the border with Lebanon, is home to some 25,000 people, according to the Syrian Observatory for Human Rights.
It is a key prize for the rebels, a conduit through which weapons and fighters can be channelled from Lebanon.
Qusayr is also important for Assad's forces because of its strategic location between Damascus and the Mediterranean coast, the rear base for the regime.
Hassan said hundreds of well-armed and organised rebels put up a fierce fight.
"It took us a long time to eliminate them," he said.
"We had to search each house or burn it. Some tunnels were destroyed but others are still there and the rebels are still hiding in them."
Over the past eight months, the Observatory says, Hezbollah has lost 104 fighters in fighting in central Homs province, which borders Lebanon, and around a revered Shiite pilgrimage site near Damascus.
Hezbollah spokesman Ibrahim Musawi denied those figures, without providing an alternative number, and a source close to the movement said it had lost 75 dead.
Despite the losses, Hassan said that the hardest was yet to come for Hezbollah, as they will have to take the town's northern neighbourhoods where most residents and rebel fighters are dug in.
"It is very difficult to take the last part. There are snipers everywhere. It will cost us dearly, but we will take it," he said with determination.
His mother Umm Hassan, 45, recalled the day her husband and son left for the battle. "When my husband left the house, I did not say goodbye to him," she said.
She maintained that the fight in Syria is vital for Hezbollah.
"It is much more important to fight in Qusayr now than against Israel because there are many (rebels) from different nationalities who are even more dangerous enemies than Israel," she insisted.
The Syrian regime says fighters from 28 countries have joined the rebels.
"My husband went to fight over there before they could attack us in Lebanon. We are not fighting against the Syrians but against our enemies who are in Syria," Umm Hassan said.