The armed officer on duty at the Florida school where a shooter killed 17 people never went inside to engage the gunman and has been placed under investigation, police has announced.

The Valentine's Day shooting at Marjory Stoneman Douglas High School by a gunman armed with an AR-15 style assault rifle has reignited national debate over gun laws and school safety, including proposals by President Donald Trump and others to designate more people, including trained teachers to carry arms on school grounds.