NEW : Police arrest Anthony Williams , 20 , in connection with the attack . Police : Man beat Mayor Tom Barrett with metal rods at the fair on Saturday . A 20-year-old Wisconsin man accused of attacking the mayor of Milwaukee with a metal pipe has been arrested , police said Sunday . Barrett heard a woman screaming and tried to help her , dialing 911 . Man who had been beating the woman then started hitting Barrett , witnesses say .
NEW : Police arrest Anthony Williams , 20 , in connection with the attack . Police : Man beat Mayor Tom Barrett with metal rods at the fair on Saturday . Barrett heard a woman screaming and tried to help her , dialing 911 . Man who had been beating the woman then started hitting Barrett , witnesses say .