"The grief of the families and loved ones is immeasurable," he said. "We must now stand together. We are all united in great grief."
The 10th grade students from the school were on their way home after a week-long Spanish exchange programme at the Institut Giola in Llinars del Valles near Barcelona.
Sylvia Loehrmann, the Education Minister for the state of North Rhine-Westphalia, said: "It was a Spanish language exchange programme and they were flying home after having what was probably the most wonderful time of their lives. It's so tragic, so sad, so unfathomable."
Along with many other residents in the town of just over 37,000, Bucker, a nursery schoolteacher, had rushed to the school when news began to emerge that some of its pupils were among those killed. "By the time I got here there were hundreds of people already standing outside, holding flowers, lighting candles, along with dozens of cameramen and photographers," she said.
"But you know what struck me? The utter silence of the crowd. You couldn't hear a sound, except for one thing - the singing of the birds. The weather is nice, it is early spring and the sun was shining. So of course the birds were singing. It was the most intensely sad, and at the same time disturbing thing I have ever experienced."