“A crowd of people were crossing the street when the first shot hit. I thought it was something like a firecracker or a car backfire until I heard the second shot and people started running,” she said.

“I saw a bullet hit the ground on the other side of the square about 30ft [9m] away before ducking into a store. The whole area was blocked off and dozens of police cars and ambulances were going towards the university.”

In a statement, Czech Prime Minister Petr Fiala said the country had been shocked by this “horrendous act”.

“It is hard to find the words to express condemnation on the one hand and, on the other, the pain and sorrow that our entire society is feeling in these days before Christmas.”

The gunman is thought to have killed his father at a separate location. He is also suspected in the killing of a young man and his two-month-old daughter who were found dead in a forest on the outskirts of Prague on 15 December.