A gunman opened fire in a crowded shopping centre Tuesday just outside of Portland, Oregon, killing two people before turning the weapon on himself.

A Clackamas County Sherriff’s spokesperson told reporters the shooter died of a self-inflicted gunshot wound.

“By all accounts there were no rounds fired by law enforcement in the mall today,” said Lt. James Rhodes.

Earlier, police confirmed that a weapon was recovered. Investigators released little information about the shooter or the victims, only indicating that the gunman was an adult male.

Officials confirmed that one other person sustained “traumatic” injuries in the shooting and multiple others were injured.

Unconfirmed reports suggest more than 60 shots were fired at the Clackamas Town Centre, located 19 kilometres southeast of Portland. Police said the shooting took place at 3:30 p.m. local time.

Rhodes said approximately 100 police officers searched the mall as hundreds of shoppers and employees remained inside the facility after the shooting took place.

“At this time the mall remains closed and we’re continue to search the mall methodically and carefully looking for anyone else who might be injured,” he said. “There are several employees and patrons of the mall who have secured themselves or have hidden in various rooms.”

The mall will remained closed until the police investigation wraps up.

Witness Holli Bautista told CNN she heard a sound “like firecrackers.”

“It was very chaotic,” she said. “People were racing towards exists and yelling.”

She said hundreds of shoppers and mall employees started running, and she and dozens of other people were trying to escape through an exit in the department store.

Bautista said the Macy's in the mall opens into the food court area, where it was reported the shootings took place.

Oregonian staff writer Rick Bella told CNN that a number of witnesses have said the shooter was wearing what appeared to be a white hockey mask and came “jogging” into the mall with what resembled an assault rifle.