After training on the pistes in the morning their 25-year-old coach took them off piste in the afternoon. He decided to attempt a steep north-easterly slope, and the 14-year-old followed him.
The boy fell and took a 15 metre slab of snow with him. None of the group were carrying safety equipment with them and it took 25 minutes to locate the teenager and dig him out of the snow. A rescue team was called and tried to revive the boy but it was too late.
The group is being questioned by police and their coach faces involuntary manslaughter charges.
There was a warning of "considerable avalanche danger" in Zillertal on the day of the accident, as well as in Karwendel, Arlberg and Ausserfern.
The risk level was four on a scale of five, meaning a single skier can set off a landslide.
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In Kühtai another skier who was off piste was swept away by an avalanche on Sunday afternoon, but he had an avalanche airbag with him and could be located and dug out within minutes.
Avalanche forecasts for Tyrol are available online at https://lawine.tirol.gv.at/home/lagebericht/