Sam, crouching behind sandbags at the Bustan al-Qasr crossing point, is the only doctor on hand to treat those targeted by the snipers.
He is 25, speaks in an urbane North American drawl and has humorous eyes twinkling above his surgical mask.
He is the son of Syrian exiles who settled in Canada. “I was in the final year of my studies to become a cardiac surgeon,” he tells me.
“On average I treat about 10 people a day, every single day, but Fridays are always the worst,” he says. “Yesterday about 30 people were shot here.”
Everybody reacts differently to the sound of the sniper’s bullet.