(CNN) A sniper who targeted cars on a Georgia highway left behind a "hate-filled" document describing the Parkland high school gunman Nikolas Cruz as a hero, a sheriff said.

Authorities identified the sniper as Rex Whitmire Harbour, 26, of Snellville, Georgia.

He shot at cars in Gainesville on Friday, leaving three people injured before he shot himself dead, Hall County Sheriff Gerald Couch said in a statement Saturday.

Harbour hid in the woods as he waited for motorists on the side of Georgia 365, Couch said. He fired at least 17 times and hit seven cars, wounding two men in the hip and leg. A third person -- a woman -- was slightly injured by broken glass, authorities said.

The two men suffered injuries that are not life-threatening, and are in stable condition.

Read More