Social Snapshot: Florida shooting and David Seymour

Another 'unspeakable tragedy' at a US school has left 17 dead in Florida.

It's been revealed Marjory Stoneman Douglas High School shooter Nikolas Cruz had a troubled past that teachers and students knew about.

Teachers were warned not to let Cruz on campus wearing a backpack as details emerged of "very disturbing" social media posts left by the teenager.

And Dancing With The Star's first celebrities have been announced. 

David Seymour and Gilda Kirkpatrick are putting their dancing shoes on for New Zealand to see.

Social Media Presenter Aziz Al-Sa'afin wraps up the biggest trends of the day. 

Watch the video.