Witness Says Missouri Teen's Hands Were Up When Cop Shot Him Missouri police say fatal shooting occurred after altercation with cop.

 -- A woman who says she witnessed the shooting of Michael Brown by a Ferguson, Mo., police officer said the 18-year-old had his hands up when he was killed.

The witness said Brown, 18, had turned around and was facing police with his hands in the air when the officer fired. She said a stray bullet from the police officer's gun hit a neighbor's home, and she was surprised no one else was injured.

"I saw him turn around with his arms up in the air and they shot him in his face and chest and he went down unarmed," Piaget Crenshaw said.

Brown's mother, Lesley McSpadden, called the shooting of her son murder, and said she hopes to see the police officer who shot him fired and that he should be put in jail.

The two spoke to ABC News after police said at a news conference that they "cannot say" how many times the teen was struck when an officer shot him after an altercation, but the young man was unarmed.

"Was the other subject, the deceased, the 18-year-old, armed with a handgun or rifle or any type of weapon at the time? The answer to that is no," said Jon Belmar, chief of the St. Louis County Police Department, which was investigating the shooting by a Ferguson Police Department officer. Police have not disclosed the name of the teen.

"It started out, the genesis of this, was a physical confrontation," Belmar said.

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The shooting Saturday afternoon in Ferguson, a suburb of St. Louis, sparked outrage, which continued today as residents marched to police headquarters to demand answers.

People in a crowd of about 200 people outside the Ferguson Police Department shouted "We want answers" and "no justice, no peace." Some carried signs saying "stop police terrorism" and "disarm the police."

Belmar said today that the incident began with when the officer allegedly had an altercation with two people, one of whom he said assaulted him in his police car.

"It is our understanding at this point in the investigation that within the police car there was a struggle over the officer's weapon," Belmar said.

According to the police chief, the officer said he then got out of his vehicle and shot "at a subject."

"There were shell casings recovered. The shell casings are all matched to one weapon, that's the officer's weapon," Belmar said. "There were more than a few shell casings recovered. I cannot say at this time how many times the subject was struck."

The officer was able to get out of the car and the fatal shooting occurred approximately 35 feet from where the vehicle was parked.

Belmar was not able to say how many times the subject was struck by police fire, but that it was more than a couple of shots.

The chief said that it was not yet clear whether the other person allegedly involved in the confrontation was armed.

The medical examiner is conducting the investigation to determine how many times the young man was shot, Belmar said.

Ferguson Police Chief Thomas Jackson contacted the St. Louis County police immediately after the shooting to have the St. Louis Police Department Crimes Investigation Force take over the investigation. He told the Associated Press that at least one shot was fired in the patrol car.

The officer who shot the 18-year-old has been with the Ferguson Police Department for six years, and has not had any other issues since he has been on the force, Belmar said. His name has not been disclosed.

He will be interviewed extensively today and will have a physiological evaluation before returning to duty, the chief said. The officer is currently on paid administrative leave.

Jackson told The Associated Press that police have contacted the second person who was involved in the altercation with the officer before the shooting, but that the person has not been arrested or charged.

The local chapter of the NAACP has called for the FBI to handle the investigation of the shooting. Belmar said that the FBI could become involved, but had not as of today.

State Sen. Jamilah Nasheed, D-St. Louis, told the St. Louis Post-Dispatch she would ask the U.S. Justice Department on Monday for a formal investigation.

ABC News' Rachel Katz and The Associated Press contributed to this report.