This incredibly sad account from the BBC:
From news article:
Rachel Gross, a high school student on board on the bus, said the gunmen opened fire as passengers fled the vehicle.
"I got down under the seats, as fast as I could, because the terrorists began firing bursts and throwing grenades, it went on and on it seemed like eternity," she said.
Yitzhak Kaufman, an Israeli paramedic who helped the wounded, told reporters: "It was a shocking scene. Women and children were lying on the floor, bleeding and screaming for help."