Associated Press reports:
The National Weather Service classified it [the tornado in Kansas] an F-5, the highest category and the first since the weather service revised its scale this year in an effort to more comprehensively gauge tornadoes‘ damage potential, with less emphasis on wind speed.
The last tornado classified as an F-5 hit the Oklahoma City area on May 3, 1999, killing 36 people.
See also here.
Update from Think Progress here.
Soldiers, police looting in Kansas tornado area.
Storm in New Jersey: here.