A Catholic priest who was a "wizard" in the Ku Klux Klan before becoming a clergyman has urged white supremacists to turn their back on hate by revealing his own personal journey from extremism.

A blizzard with hurricane-force winds brought much of the US East Coast to a standstill today, dumping as much as three feet of snow, stranding tens of thousands of travellers and shutting down Washington and New York City.

Shoppers raided grocery and hardware shops, bishops excused Catholics from Mass, and the capital shut down ahead of a snow storm that will blanket much of the Eastern US this weekend.

A man carrying a shotgun opened fire at a busy US shopping mall, killing two employees of a skate shop and then himself as panicked shoppers ran for cover.

The coldest, most dangerous blast of polar air in decades has gripped the US midwest and pushed toward the east and south and eastern Canada.