DENVER -- Police breaking up a gunfight in the popular Lower Downtown area shot and killed one man and critically wounded another man after both allegedly fired a shotgun at the officers early Sunday.

Police Lt. Ron Saunier said the officers were on routine duty helping crowds move out of LoDo as clubs were closing when they saw a fight begin. He noted "there are thousands upon thousands of people" in the area almost every night when clubs close at 2 a.m.

As the officers approached, two individuals began exchanging gunfire, Saunier said.

"We were trying to get to our car and all we heard was pop, pop, pop, pop," said Curtis Deleon. "So we hit the deck."

One man with a shotgun opened fire on the two officers, she said, forcing the officers to return fire and kill him.

"Then there was a slight pause so we ducked around, looking around, trying to figure out what going on and then there were several more rounds," said Meghan Aspden. "So everybody was kind of hiding, a little bit of a war zone looking around and eventually there was a car and it came squealing out."

A second man picked up the shotgun and started firing at police and was then hit as officers fired back.

Both men were taken to Denver Health Medical Center where the first gunman died of his injuries. The second gunman is in critical condition, police said.

Four other people were injured by shotgun pellets but are expected to survive, Saunier said.

Police are looking for a third man who was firing a handgun during the firefight.

People who work in the area said although it is unusual to hear gunfire, fights occur downtown somewhat frequently.

"It has always been scary down here at 2:00 in the morning," said Shyela Marqued "Always a pretty sketchy situation down here that time of the night."

The officers, who were put on administrative leave as is practice after fatal shootings, did not suffer any injuries.

The last fatal shooting in the LoDo area was in November.

Saunier said crime in Denver is down, although he had no specific figures for LoDo.

Anyone with information about this incident is asked to contact the Denver Police Department at 720-913-2000 or anonymously through crime stoppers at 720-913-STOP (7867).