ST. ANN -- An off-duty Berkeley police officer, shopping at Northwest Plaza, shot and killed a man after a confrontation in a clothing store shortly before 2 p.m. Wednesday, authorities said.

Police did not reveal the name of the officer or the man he killed.

St. Louis County police issued a statement saying the man "bumped" the officer several times in the mall in St. Ann, and that when the officer entered the Man Alive store on the mall's southern end, the man followed and bumped him again.

The officer, in plain clothes, told the man he was under arrest, according to the statement. A struggle ensued, the man tried to take the officer's gun, and the fearful officer fatally shot him, authorities said.

The officer was treated for a minor hand injury, police said. No one else was injured.

Police would not release any other information. There were no details of what led up to the shooting, whether the two were acquainted and whether the man who was killed had been armed.

An assistant manager of the store, who spoke on the condition that his name not be used, said he noticed the officer and a man arguing when they entered the store. He said he heard the officer yell, "Well, do something about it."

He said he saw the man spit at the officer, who drew his weapon and chased the man around the store. The man was backing away, pulling racks over to block the officer's path, the manager said.

The men struggled, moving into an emergency exit hallway behind the store. The manager said he closed the door and then heard shots.

Berkeley police Maj. Frank McCall said the officer was placed on administrative leave pending an investigation but declined further comment.

St. Ann police referred inquiries to county police, whose detectives usually investigate shootings by municipal officers.

Arriving officers from St. Ann and Berkeley swarmed the mall and told people to take cover, witnesses said. Several mall employees said they locked their stores' doors when they saw police.

"When I see guns, I just go into a defense mood," said Lashawnda Luster, 32, who closed the doors at her store, called Rave.

"I just can't believe this happened at a mall," Luster said.

The mall, at Lindbergh Boulevard and St. Charles Rock Road, has fallen on hard times in recent years with the declining popularity of enclosed malls and the emergence of new competition.

Somera Capital Management LLC, a private equity firm based in California, bought Northwest Plaza in June for $45 million from Westfield Group of Australia. An official with Somera has said it is planning a major overhaul.

The mall opened in 1965.

In 2003, it began requiring anyone 17 or younger who is there after 6 p.m. to be accompanied by a parent, guardian or adult at least 21 years old. At the time, mall officials and police said the measure was to restore a family atmosphere and stop teen loitering and occasional skirmishes.

"We're not against having kids in the stores, but we want families here, not roving bands of juveniles," St. Ann Police Chief Bob Schrader said then.

At the time, Schrader told the Post-Dispatch that over the years, St. Ann police had tried various options to keep peace at the mall, including stationing mounted police in the parking lots and patrol officers on rooftops.

Elizabethe Holland and Heather Ratcliffe of the Post-Dispatch contributed to this report.