Oklahoma tornado: how did it form and why was it so deadly?

Briefing Tue 21 May, AT 16:07

Twister was a category four storm that struck the suburb of Moore with just five minutes' warning

Deadly Joplin tornado captured by storm chasers

Video Tue 24 May, AT 12:23

Twister is caught on video from car as it rips through Missouri town, plus the immediate aftermath (with video)