Will arming teachers with guns stop US school shootings?

President Donald Trump has said that if one of the victims of the latest school shooting in the US, a football coach, had been armed "he would have shot and that would have been the end of it".

Revisiting an idea he raised in his presidential campaign, Mr Trump's comments in favour of allowing teachers to be armed come as politicians in several states are wrestling with the idea, including in Florida, where the 17 most recent school shooting victims are being mourned.