Multiple people were shot on Wednesday inside a Walmart in a Denver suburb, local police said.
Police in Thornton, Colorado, did not release any information about any of the victims and it was not clear if an assailant had been taken into custody. Thornton is about 10 miles (16 km) northeast of Denver.
"We've got multiple parties down, we're still trying to ascertain what their conditions are," Officer Victor Avila of the Thornton Police Department told Reuters.
The store had been "self-evacuated" by customers and employees who fled following the gunfire, Avila said.
Reports of shots fired came shortly before 6:30 p.m. Mountain Time, a police spokesman told local 9NEWS in Denver.
Local television images showed a number of police cars and ambulances surrounding the store, lights flashing.