FERGUSON, Mo. — Conditions calmed this week in Ferguson after nights of sometimes violent unrest stemming from the fatal shooting of a black 18-year-old by a white police officer. But a delicate and crucial question lingers: What happens if the grand jury now considering the case doesn’t return a charge against the officer?

The fear among some local residents and officials trying to maintain peace in Ferguson is that failure to charge the officer could stoke new anger among a community profoundly mistrustful of the legal system. Many say they just hope the grand jury’s decision, whatever it is, has irrefutable facts to back it up.

U.S. Sen. Claire McCaskill told The Associated Press she’s pushing for federal and local investigations to be completed around the same time so that all evidence in the case can be made public – a step many consider important should prosecutors decide not to charge the officer. Her office said Friday that the Department of Justice hasn’t given a timeline for the federal investigation, which centers on whether a civil rights violation occurred when Officer Darren Wilson fatally shot the unarmed Michael Brown Aug. 9.

‘INCONTROVERTIBLE FACTS’

McCaskill, a former prosecutor in Missouri, said she’s hopeful the physical evidence in the case – including blood spatter patterns, clothing and shell casings – will provide “incontrovertible facts” about what happened during the shooting. She said whatever local prosecutors decide, it will be important to explain the decision by providing that physical evidence, and that won’t be possible if the federal investigation is ongoing.

McCaskill said she urged Attorney General Eric Holder during a meeting earlier this week to speed up what is typically a lengthier federal process.

“What we want to avoid is a decision being made without all the information being available to the public also,” McCaskill said, adding that not being able to do so could “create more stress and certainly much more fear that we would be back to worrying about people being able to protest safely.”

“Obviously all of us are concerned not just about that this process be fair, but what does this next six months look like?” she said.

‘YOU’VE GOT TO GET IT RIGHT’

Gov. Jay Nixon didn’t say if he agreed with McCaskill’s call to conclude both investigations at the same time. He said the full focus is on seeking justice.

“To me it’s one you’ve got to get right. Just got to get it right,” he said.

Many residents who live in the Ferguson area, eager to end the disruptions to their lives caused by protests and police presence, say they fear the community’s anger will explode anew if Wilson isn’t charged.

“This officer has to be indicted. I’d hate to see what happens if he isn’t. The rioting, the looting, man …” said resident Larry Loveless, 29, as he stopped at the memorial for Brown.