Details emerge of how 21-year-old planned school attack in which teacher and nine pupils were killed

A gunman who killed 10 people at his former school in the Austrian city of Graz was an “obsessive online first-person shooter”, according to police, who gave detailed information for the first time about how he had planned the attack.

The 21-year-old Austrian, who shot dead 10 people and then himself on Tuesday morning after going on a rampage at the school close to the city centre, had spent much of his free time playing what were described by police as “ego shooting” online video games, in which participants typically use virtual firearms to kill enemies.

Police said they believed the online community of players had formed his main social contacts and that he had otherwise been a loner who kept to himself.

It emerged that among the people killed by the man, identified by the Austrian and German media as Arthur A, was one of his former teachers. Police said it was unknown if he had deliberately targeted her.