Sky correspondent Rachael Venables has arrived in Graz this evening.
She said the “question on everyone’s mind” in the city is what the gunman’s motive was for the attack.
However, she said there have still been “no updates from the authorities”.
Austria’s interior minister Gerhard Karner said earlier that the gunman was a former pupil who didn’t finish school.
Rachael continued: “We know that he is understood to have been a 21-year-old who was living locally.
“But no more information about any form of motive, whatever it might have been, that could lead somebody to such hideous acts”.
As Rachael spoke, people were laying lit candles outside the school as a tribute to the victims.
She continued: “Many people in this local area, they tell me they heard the gunshots, they thought at first it was innocent noise – and then after the beats came further and faster and louder, they realised something was dreadfully wrong.
“This really is a community in mourning.”
Number killed in Austria school shooting rises; police release details of gunman