A confrontation between police and protestors turned violent Saturday night in Milwaukee in the north-central U.S. state of Wisconsin, after a police officer shot and killed an armed 23-year-old man.

A gas station and a vehicle were set on fire after some 100 protestors gathered near the scene of the shooting and confronted with the police for about an hour earlier in the evening.

A police officer was hit in the head by a brick thrown through the car's windows.

The shooting happened Saturday afternoon when two police officers pulled over a car with two suspects inside. The suspects then began to run. In a foot chase, a police officer shot and killed the 23-year-old, Milwaukee Journal Sentinel reported.

The police officer was not hurt, but was placed on administrative leave while an investigation into his conduct has been launched.

The second suspect, also a 23-year-old man, has been in custody.

In a news briefing at the scene shortly after the shooting, Milwaukee Police Assistant Chief Bill Jessup said the man who was killed carried a stolen handgun and has "a lengthy arrest record," which he failed to specify.

The incident was preceded by several police-involved shootings across the United States, in which the use of force by police is questioned.

In July, two black men were shot dead by police in Louisiana and Minnesota, which sparked angry protests by African Americans across the nation against police brutality and racial discrimination.

Earlier this year, a native American woman was killed by an Arizona police officer. The shooting has prompted protests in recent months by Native American activists.