Larry Copeland, Yamiche Alcindor and Melanie Eversley

USA TODAY

ST. LOUIS — A 23-year-old male robbery suspect is dead after allegedly waving a knife at police, screaming at them to kill him and then being shot by an officer in north St. Louis, authorities said Tuesday.

The incident took place about 4 miles from unrest in suburban Ferguson, where protests and clashes continue following the Aug. 9 fatal shooting of an 18-year-old man by local police. The incident Tuesday did not appear to be related to Ferguson, although a crowd that gathered appeared to have questions, prompting two aldermen at the scene to urge calm. No officers were injured, authorities said.

In a news conference, St. Louis Police Chief Sam Dotson confirmed the shooting in the city's Sixth District. The suspect came within 3 or 4 feet of two police officers and "brandished a knife" during a convenience store altercation and yelled, "Shoot me; kill me now," Dotson said.

Some witnesses described the incident as "suicide by cop" — a situation in which someone with a death wish engages in activity that may prompt a law enforcement officer to shoot at them — but Dotson said he did not agree.

The suspect walked into a convenience store, stole some energy drinks, walked out, walked back in again and stole some pastry, Dotson said.

According to witness Robert Addison, the suspect attempted to walk out with donuts and something to drink and when the proprietor told the suspect that he'd stolen the goods. The suspect then " the suspect "responded by throwing down the food and shouting, 'I don't need this,' " Addison recounted.

The store owner called police as the man paced in front of the store, Dotson said. When police arrived, the man "brandished a knife," Dotson said.

Addison said the suspect walked to the driver's-side door of the police cruiser and screamed, "You are going to have to kill me before you take me to jail."

Police asked the man if he had a weapon and the man produced an object, Addison said.

From about 7 or 8 feet away from the officers, the man continued to scream and the officers yelled at him to freeze, according to Addison. When the man took a "half step" toward the police, they fired, each firing about five times, Addison said.

Witness Aaron Morris described the suspect as a mentally challenged man with a "child-like mind." He said he believes the police overreacted.

"I feel like it's an example of law enforcement overextending its power," said Morris, 30, of St. Louis.

The suspect was black, the officers were white according to Addison, and the incident prompted St. Louis aldermen Antonio French and Chris Carter to urge people at the scene to remain calm.

"Let's be patient," French said. "The last thing we need is violence in our neighborhood. No silliness over here. We're going to find out what happened. You've got people that got your back over here. You aren't alone like they are in Ferguson."

Ferguson's population is two-thirds African American, but the local government and police department are predominantly white.

Carter said they were there to "ask people to stay calm and to wait on the facts of the investigation."

As French and Carter tried to calm emotions, several people in the crowd shouted questions about why the officers didn't use Tasers instead of guns. There also were repeated chants of "Hands up! Don't shoot!" That has been the rallying cry of the protesters in Ferguson in response to the Michael Brown shooting.

Contributing: Donna Leinwand Leger in Washington; Linda Dono in McLean, Va.; Brandie Piper of KSDK in St. Louis. Eversley reported from New York.