The Austrian school shooter who massacred 10 people at his former school on Tuesday killed his neighbour in the horrific attack, it has emerged.

Artur A., a 21-year-old from a suburb of Graz, was revealed to have shot and killed a young girl who lived nearby as further details emerged of his abandoned plans to carry out a bombing and messages left behind for family.

The former student of the school killed a teacher and nine pupils between the ages of 14 and 17 in Tuesday's rampage in the city of Graz.

A further 11 were seriously injured before Artur took his own life at the BORG Dreierschützengasse high school.

The first victim was identified as 15-year-old Lea Ilir Bajrami earlier today.