A gunman opened fire Thursday at a grocery store in Collierville in the U.S. state of Tennessee, killing one person and injuring at least 12 others before shooting himself to death, police said.

Collierville Police Chief Dale Lane told a news conference that police arrived at the Kroger store in the Memphis suburb at 1:34 p.m. local time, about four minutes after receiving a report of the shooting, to help escort the victims and evacuate the area.

The attacker had died and was believed to have been killed by a self-inflicted gunshot wound. 

The injuries to the victims were "very serious," the police chief said. 

"We found people hiding in freezers and in locked offices," Lane said, calling the gun violence "the most horrific event that has occurred in Collierville history."

Neither the victims nor the suspect were immediately identified and the motive of the shooter remains unclear.

Some local media reported the shooter was an employee, citing unnamed law enforcement sources.

Thursday's violence was the latest in a string of deadly workplace mass shootings that have erupted in U.S. cities, claiming dozens of lives and leaving many more wounded this year.

Ten people were killed in March when a gunman opened fire at a supermarket in Boulder, Colorado.

(With input from Xinhua and Reuters)