Vienna police have released a request from the public to withhold from posting videos and photos of the incident on social media.
They said this endangers both emergency services and the civilian population.
In addition, the police ask those who do have videos to send it to the police: "If you have footage of any kind of the shooting incident in the inner city of Vienna – please upload it on this link (active on Twitter) – DON’T share it on social media! This way you can support us!"