According to Lower Saxony police the 32-year-old Hanover 96 was hit by a train at a crossing early on Tuesday evening, leaving fellow players, coaches and fans stunned by the news of his death.
"This can and must not be true," said Schalke 04 striker Kevin Kuranyi. "Robert was a fantastic guy."
Hamburg SV captain David Jarolim told Bild newspaper he is devastated.
"I can hardly breathe. This is a real tragedy, first his daughter and then this," Jarolim said.
Enke's two-year-old daughter died in 2006 due to a heart ailment, her death triggering an outpouring of sympathy for the family at the time.
"I am endlessly saddened by this," former Germany coach Franz Beckenbauer said. "When you receive such news all other things do not matter."
Enke, who was in the running to be Germany's starting goalkeeper at next year's World Cup in South Africa, had been at Hanover since 2004.
"This is terrible. I am not able at the moment to express myself in more detail," said Hanover 96 sports director Joerg Schmadtke.
German national team manager Oliver Bierhoff said the team, gathered ahead of a friendly match against Chile in Cologne, is in a state of shock."
"We are just all speechless," said Bierhoff.
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