"We were shocked when we heard," Germany assistant coach Hansi Flick told reporters on Tuesday. "Team manager Oliver Bierhoff talked to him and we wish him a quick recovery.
"We were told that it was during the shooting but I do not know more. He played a superb season and it is also a major loss for Eintracht."
The injury is certain to infuriate Eintracht given it did not take place on the pitch.
"I think the sports side should always be at the forefront," said Borussia Dortmund's Germany international Mario Gotze. "I have done shoots myself but none that were dangerous. But I think we should always stay healthy at such events."
Trapp, who has played every game this season, has been outstanding as the promoted club lie in fourth place in the Bundesliga and challenge for a Champions League spot.
"First diagnosis is that of a hand fracture. He is set to return to Frankfurt today to have his diagnosis confirmed by Eintracht team doctor Christoph Seeger," Eintracht said in a statement.
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