THORNTON, Colo. (AP) — A man nonchalantly walked into a Walmart and immediately opened fire with a handgun, killing two men and a woman before fleeing in a car on Wednesday night, according to Colorado authorities.

The shooting appears random and there are no indications that it was an act of terror, said Thornton police spokesman Victor Avila.

“This is a very heinous act,” Avila said. “We don’t know exactly what the motive of the person was, but it was certainly a terrible act.”

Two men died inside the Walmart, which is about 10 miles (16 kilometers) north of Denver in a busy shopping center. The woman died later at a hospital.

Aaron Stephens, 44, was in the self-checkout line when he heard a single shot followed by two more bursts of gunfire before people started running for the exits.

“The employees started screaming. Customers were screaming. They were running like crazy, and I ran out too because I didn’t want to get killed,” he said.

Guadalupe Perez was inside the store with her young son when she heard what she thought was a balloon popping. A Walmart employee told her someone was shooting, and then Perez saw people running away yelling, “Let’s go. Let’s go. Leave the groceries.”