Updated

Missouri Gov. Jay Nixon drew criticism from his own Lt. Governor Tuesday when he said "a vigorous prosecution must now be pursued" in the shooting death of black 18-year-old Michael Brown by white police Officer Darren Wilson in the St. Louis suburb of Ferguson.

Nixon made the comment in a videotaped statement in which he said he would not remove St. Louis County Prosecutor Bob McCulloch from the case despite the demands of some black leaders who believe that McCulloch's deep family ties to law enforcement would affect his impartiality. McCullouch's father, mother, brother, uncle and cousin all worked for the St. Louis Police Department, and his father was killed while responding to a call involving a black suspect.

In his statement, Nixon cited what he called the "well-established process" by which prosecutors can recuse themselves from pending investigations to make way for a special prosecutor. Departing from that process, Nixon said in a statement, "could unnecessarily inject legal uncertainty into this matter and potentially jeopardize the prosecution."

"We have a responsibility," Nixon said, "to come together, and do everything we can to achieve justice for [Brown's] family." Nixon added that McCulloch and U.S. Attorney General Eric Holder had an obligation "to achieve justice in the shooting death of Michael Brown must be carried out thoroughly, promptly, and correctly."

"It's really heartbreaking to see a man elected to an office that high in our state government  ... come out with a statement like that, that does prejudge the case," Missouri Lt. Gov. Peter Kinder told Fox News' Shepard Smith late Tuesday. "It would be wrong for a prosecutor to say what the governor has said here tonight and it's wrong for the governor of Missouri to have said it."

Nixon and McCulloch are Democrats, while Kinder is a Republican. Under Missouri law, the governor and lieutenant governor are elected separately.

Sgt. Kevin Ahlbrand, President of the Missouri Fraternal Order of Police, told Fox News' Megyn Kelly that he was "very disappointed" in the governor's statement.

"We welcome a vigorous investigation," Ahlbrand said. "Unfortunately, justice needs to go both ways. Darren's been vilified in the press and by politicians with minimal facts being made public."

A grand jury could begin hearing evidence Wednesday to determine whether Wilson should be charged in Brown's death, said Ed Magee, spokesman for St. Louis County's prosecuting attorney.

The streets of Ferguson filled once more with protesters Tuesday evening, but the scene was much more subdued than on any of the previous five nights, with smaller crowds. For many hours, the protest was lively but peaceful. After midnight, tensions rose as officers tried to remove the relatively small number of protesters who had not left. Bottles were reportedly thrown, resulting in police chasing some demonstrators through the streets.

Missouri Highway Patrol Capt. Ron Johnson said early Wednesday that police had made 47 arrests overnight. However, Johnson said that no Molotov cocktails were thrown at authorities and no shots were fired by police or protesters. Three handguns were confiscated, including two from a vehicle from which a threat to kill police officers had been made.

Earlier in the day, Ferguson city leaders urged people to stay home after dark Tuesday to "allow peace to settle in." In his press conference, Johnson credited local residents, activists, and clergy members with creating what he called a "different dynamic" and helping to dilute the confrontational atmosphere that had marked most of the past nine days. He noted that police had not used tear gas or smoke canisters Tuesday night, adding that people "protested early, and went home early."

The calls for calm were echoed by Holder in an open letter published on the St. Louis Post-Dispatch website late Tuesday. The Attorney General said the Justice Department would "will defend the right of protesters to peacefully demonstrate and for the media to cover a story that must be told," and implored the citizens of Ferguson "to join with law enforcement in condemning the actions of looters, vandals and others seeking to inflame tensions."

In a public statement earlier Tuesday, the city said the mayor, the City Council and employees have been exploring ways to increase the number of African-American applicants to the law enforcement academy, develop incentive programs to encourage city residency for police officers and raise money for cameras that would be attached to patrol car dashboards and officers' vests.

The Associated Press contributed to this report.