Demonstrations in Ferguson, Missouri, over the killing of Mike Brown will stop only when the cop who shot him is prosecuted, Brown's parents said Tuesday morning on the “Today” show. Nevertheless, Michael Brown Sr. and Lesley McSpadden also spoke out against the violence and looting in the St. Louis suburb.

“Justice will bring peace,” McSpadden told Matt Lauer of  NBC's “Today,” calling on authorities to arrest Darren Wilson, the Ferguson police officer who shot her son on Aug. 9.

She said the violence, including looting and a report of two people shot in Ferguson Monday night, takes away from the purpose of the protests.

“Violence needs to stop. … It is a distraction,” she said.

“We need to keep the focus on Michael Brown Jr.,” Brown’s father added.

Capt. Ron Johnson of the Missouri State Highway Patrol, the agency now overseeing Ferguson, blamed the violence on “criminals” and not protesters. He said Molotov cocktails were thrown at officers and gunfire was directed at them Monday night, but police didn’t fire any bullets back. Some of the 31 people arrested were from out of town, including New York and California, he told NBC News.

"These criminal acts came from a tiny minority of lawbreakers," he said. "It is criminals who throw Molotov cocktails, fire shots and endanger lives. These are not acts of protesters, but acts of violence."