Investigators say the man, 21, was a recluse “unwilling to participate in normal activities outside in the real world.” Officials are asking how he passed a psychological test for a gun permit.

© Darko Bandic/Associated Press

The deadliest school shooting in the nation’s recent history has prompted some gun enthusiasts to worry about the prospect of stricter ownership laws.

© Kleine Zeitung/Associated Press

A former student killed 10 people and then himself in a shooting in Graz on Tuesday, the police said. The authorities said a pipe bomb and a “farewell letter” were found at the shooter’s house.

© Borut Zivulovic/Reuters

The attack in the city of Graz was among Europe’s worst school shootings in years. The police said the gunman also died, in an apparent suicide.

© Erwin Scheriau, via Agence France-Presse — Getty Images