It cost him his life.
Witnesses said the Palestinian doctor rushed to help the wounded lying around a car struck by a missile.
But he himself was hit by shrapnel when a second missile slammed into a crowd of people who had also come to see who they could save.
“Doctor Zain rushed to help, and he paid with his life trying to save the lives of others,” store owner Hisham Muhammad told Reuters. “He treated a few people on the ground before he... fell among them.”
Medical officials said eight people, all civilians, were killed and about 70 wounded in the airstrike, one of five carried out by Israel in the Gaza Strip on Monday.
“The Palestinian Authority should quit talks about peace and ceasefires and everyone must fight until either we achieve victory or martyrdom”
Ali - protester
Shahin, 29, was married to a Russian and had two children.
Women wept as rescue workers carried the wounded to hospital, while men chanted Allahu Akbar (God is greatest).
Thousands of protesters in the Nusayrat refugee camp, a stronghold for armed fighters, called for revenge and urged Prime Minister Ahmad Quraya to abandon efforts to make peace with Israel.
“The Palestinian Authority should quit talks about peace and ceasefires and everyone must fight until either we achieve victory or martyrdom,” said another protester, who gave his name only as Ali.
Witnesses said each missile had lit up the night sky.
“It lit the street, like lightning, but the sound was thunderous,” one witness said.
Another witness, Mahmud Al-Qassas, was in deep shock.
“What can I say? It was unbelievable to bear what I saw,” he said. “Where are the United States and the United Nations? Are not we humans and have rights? Why do they keep silent to see us being massacred.”
It was the bloodiest of the five air strikes on Monday. An earlier attack killed two Islamist fighters and a bystander in Gaza City.