Former U.S. senator and presidential candidate Carol Moseley Braun suffered a broken wrist when a mugger tried to steal her purse, authorities said Saturday.

Braun, 59, was standing at her front door late Friday when an assailant came out of the bushes and tried to take her purse, said her spokesman, Kevin Lampe. When Braun resisted, the man pulled a knife and cut the strap of the purse.

During the struggle, Braun fell, fracturing her left wrist. She was later treated and a released from a hospital.

A student from the nearby University of Chicago came to her aid, Lampe said.

Zachary Trayes-Gibson said he had been walking with a friend when he heard screams.

"I turned to look and saw a woman on the ground and a man on top of her assaulting her," Trayes-Gibson said. "It looked like he was throwing punches. I turned and ran toward them, and my friend yelled out 'Hey!' and he (the assailant) looked up."

After the attacker ran off, Trayes-Gibson was surprised to learn who he was helping.

"He is the hero of the day," Lampe said.

Braun's assailant fled the scene without the purse, Lampe said. He remained at large Saturday, said Chicago Police spokeswoman Officer JoAnn Taylor.

Braun, a Democrat, became the first black woman elected to the U.S. Senate in 1992, serving one term. She lost her re-election bid to Peter Fitzgerald in 1998. After her defeat, President Clinton appointed her ambassador to New Zealand and Samoa. She made a run for the presidency in 2004.