The trench coat-clad gunman who killed five people and wounded four at a shopping mall before being fatally shot by police calmly fired a shotgun at his victims and had a handgun, authorities and witnesses said.

Detectives were trying to determine what sparked the rampage at the Trolley Square shopping mall on Monday night.

Salt Lake City police Detective Robin Snyder said the shooter was an 18-year-old from the Salt Lake City area, but she did not release his name. She said he used a shotgun and had a handgun and several rounds of ammunition.

As investigators interviewed 100 to 200 witnesses, people left candles and flowers at two memorials outside the mall for the victims.

Many people forced to leave their cars overnight returned Tuesday to pick them up and reflect on what happened.

"I've worked here for 28 years. It's been the safest place to be," said Steve Farr, who saw pools of blood and broken glass throughout the mall when he was allowed in to check his jewelry store.

Marie Smith, 23, a Bath & Body Works manager, said she had seen the gunman through the store window. She watched as he raised his gun and fired at a young woman approaching him from behind.

"His expression stayed totally calm. He didn't seem upset, or like he was on a rampage," said Smith, who crawled to an employee restroom to hide with others. He looked like "an average Joe," she said.

Killed in the attack were two 28-year-old women, a 52-year-old man, a 24-year-old man and a 15-year-old girl, Snyder said. Four people were hospitalized — a man and a woman in critical condition and two men in serious condition, Snyder said.

For hours after the rampage, police searched stores for scared, shocked shoppers and employees who were hunkered down awaiting a safe escort.

Matt Lund was visiting his wife, Barbara, manager of the Secret Garden children's clothing store, when he heard the first shots. The couple and three others hid in a storage room for about 40 minutes, isolated but still able to hear the violence.

"We heard them say, 'Police! Drop your weapon!' Then we heard shotgun fire. Then there was a barrage of gunfire," said Lund, 44. "It was hard to believe."

Witnesses said officers treated everyone like suspects — ordering those hiding in storerooms, bathrooms or under stairwells, to lie on the floor with their hands on their heads until police were sure no one posed a threat.