“Lately it looks like a war zone and that is not acceptable,” Governor Jay Nixon said of Ferguson, outside St Louis, where county police have been criticized for their military-style crackdown on protests.
“We will all need to join hands to rebuild the trust that’s been lost and help this community regain its stability,” Nixon said, appointing a local African-American officer, Captain Ron Johnson, to take charge.
Michael Brown, an 18-year-old African-American who was due to start college two days later, was shot dead by county police on Saturday.
Witnesses and police have given conflicting versions of how the fatal shot was fired, and anger over the killing triggered angry protests.
Local officers responded by donning military-style combat uniforms, arming themselves with assault rifles, tear gas and rubber bullets, and deploying armoured vehicles to crush dissent.
The reaction was criticised as heavy-handed and over-militarized by critics from across the political spectrum – from civil rights leaders to Republican Senator Rand Paul to President Barack Obama.
Nixon reacted on Thursday by standing down the St Louis County police who had led the crackdown, and drafting in the Missouri Highway Patrol, which answers to the state government.
Johnson, who takes charge of security, said police would show respect to the citizens as they try to restore calm.
“I grew up here and this is currently my community and my home. It means a lot to me personally that we break this cycle of violence and build trust, and show the utmost respect,” he said.
“I understand the anger and fear that the citizens of Ferguson are feeling, and our police officers will respect both of those.”
Nixon, however, did not cede to one key demand of the protesters. Control of the investigation into the police shooting of Brown will remain in the hands of the St Louis County force.
The US Department of Justice has already announced a separate federal investigation into whether the mainly white force had committed a civil rights violation in the majority black town.