Sharon Otis, left, and her son Jonathan Johnson, both of Ferguson, Mo., help clean up a strip mall Tuesday after it was damaged by rioters.

FERGUSON, Mo. — Attorneys for Michael Brown’s family vowed Tuesday to push for federal charges against the police officer who killed the unarmed 18-year-old, and they renewed calls for peace following a night of violent protests in which several businesses burned to the ground.

As darkness fell, hundreds more National Guardsmen were ordered into Ferguson in hopes that their presence would help local keep order.

The attorneys said the grand jury process was rigged from the start to clear the white officer, Darren Wilson, in the Aug. 9 shooting death of Brown, who was black. They criticized everything from the evidence the St. Louis County prosecutor presented to the jury to the way it was presented, as well as the timing of the announcement of the grand jury’s final decision.

“We said from the very beginning that the decision of this grand jury was going to be the direct reflection of the presentation of the evidence by the prosecutor’s office,” attorney Anthony Gray said. He suggested the county’s top prosecutor, Bob McCulloch, presented some testimony to discredit the process.

They hope a federal civil rights investigation results in charges against Wilson.

Twelve commercial buildings in Ferguson burned down during protests that erupted after the grand jury’s decision was announced, and firefighters responded to blazes at eight others, fire officials said. Other businesses were looted, and 12 vehicles were torched.

By Tuesday afternoon, several businesses along West Florissant Avenue, scene of many of the most intense clashes, were already closed.

Natalie DuBose, owner of Natalie’s Cakes and More, planned to spend Tuesday night at her business.

“I have to be here because I have orders that I have to complete for tomorrow and for Thursday because of the holiday. I just couldn’t do it today because of the cleanup.”

A window at her business was busted out.

“I’m emotional because of what has happened to me,” she said. “This is my livelihood. This is the only source of income I have to raise my children.”