A 36-year-old Louisiana sheriff's deputy was directing traffic in a school zone Thursday morning when he was shot three times by a man whose motive remains a mystery, authorities said.

Cpl. Burt Hazeltine was in stable but guarded condition at a New Orleans hospital, St. Charles Parish Sheriff Greg Champagne said.

Hazeltine was directing traffic in the town of Paradis, about 25 miles west of New Orleans, when a man parked a pickup truck at a nearby convenience store, got out and opened fire, Champagne said.

A suspect, whose identity hasn't been released, was arrested a short time later. He is believed to be the only person involved, Champagne said.

Hazeltine is believed to have returned fire, but it was unclear whether the suspect was hit. St. Charles Parish authorities planned an afternoon news conference.

Hazeltine was alert and able to talk with emergency medical personnel at the shooting scene, Champagne said.

"His vital signs are good. There is some bleeding in the chest. They're monitoring that closely," Champagne said.

Two nearby schools were briefly placed on lockdown after the shooting.