A gunman fatally shot a man and a woman outside a Walmart in Duncan, Okla., on Monday morning, then killed himself, the police said.

At a news conference on Monday afternoon, the Duncan Police Department’s chief, Danny Ford, said that the gunman had approached a man and a woman in a car in the parking lot in front of the Walmart, about 80 miles south of Oklahoma City, before 10 a.m. The pair had apparently visited the money center inside the store just beforehand. Investigators believe the gunman fired several rounds at the two and then turned the gun on himself, Chief Ford said.

All three were pronounced dead at the scene. A semiautomatic handgun was found at the scene.

Chief Ford said investigators had identified the individuals involved, but would not release their names because not all of the families had been notified. One of the victims is believed to have been or is currently a Walmart employee, he added.

The motive is not yet known, Chief Ford said. It appeared that the victims and gunman knew each other, he said. Investigators have spoken to several witnesses and are reviewing surveillance footage.