SWAT teams surrounded the Denver Safeway Distribution Center Sunday after reports of a gunman on the loose.
Denver Police Chief Gerald R. Whitman says they received first reports that a man was shooting people in the produce section.
"They narrowed down where this guy was through repeated 911 calls inside."
When police forces moved in, they discovered the suspect was not only taking shots but also setting fires throughout the building.
Smoke poured from vents and open doors as about 150 employees rushed outside to safety.
Inside, police found one employee dead and four who had been injured. They also found the gunman.
"The officers confronted the suspect who was armed with a handgun, he fired at us and we fired at him," said Chief Whitman.
When the shooting stopped, the suspect lay dead and one officer was in serious condition with a gunshot wound to the hip.
Police say they anticipate a lengthy investigation because between the fires and the shootings the alleged gunman caused extensive damage to the warehouse and police must interview every employee who witnessed it.
Police and officials at Safeway are still trying to confirm the suspect's identity, but say they believe he is an employee hire early last year.
At this point, they have no idea what motivated the attack.
"Whenever workplace violence occurs, you really have to take a step back and look at everything you are doing."
Officials at Safeway say their main concern now is caring for wounded employees who are still in serious and critical conditions.