US presidential candidate Ben Carson's staff killed in fatal car accident

Republican presidential candidate Ben Carson cancelled public events on Tuesday after a van carrying three volunteers and a campaign staffer slid on ice in Iowa, flipped on its side and was hit by another vehicle, his campaign said.

One of the volunteers, Braden Joplin, 25, died after being taken to a trauma centre at the University of Nebraska Medical Centre in Omaha, the hospital said in a statement released by the Carson campaign. The other three people were treated and released from a hospital in Atlantic, Iowa, the statement said.

Rest In Peace Braden Joplin. Our thoughts and prayers are with his family. pic.twitter.com/p87TCnD44p

— Dr. Ben Carson (@RealBenCarson) January 20, 2016

Carson, a retired neurosurgeon, was travelling from South Carolina to Omaha where he planned to meet with Joplin's family members and offer his condolences, the hospital statement said. Carson is among a dozen Republican presidential candidates crisscrossing Iowa before the state's February 1 caucuses, the nation's first contest to determine the party's nominee in November's presidential election. 

Democratic frontrunner Hillary Clinton tweeted a condolence message to the Joplin family:

I'm so sorry to hear about this terrible tragedy. My heart goes out to Braden's family and colleagues. -H https://t.co/zqI0JBfiJ5

— Hillary Clinton (@HillaryClinton) January 20, 2016