Tulsa police officer acquitted in death of unarmed African-American man

— -- A white police officer was found not guilty on Wednesday in Tulsa, Oklahoma, in the 2016 shooting death of an unarmed black man

About 100 demonstrators gathered near the courthouse where a jury acquitted Tulsa police officer Betty Shelby of first-degree manslaughter charges in the 2016 shooting of 40-year-old Terence Crutcher.

After the decision was announced, peaceful but defiant protesters briefly blocked an intersection in downtown Tulsa, prompting authorities to threaten the use of tear gas and arrest. The crowd eventually dispersed overnight.

Demonstrators chanted, "No Justice, No Peace" and "Hands up, don't shoot!" in the streets.

Oklahoma Gov. Mary Fallin called for peace after the verdict came down.

"Those who disagree with the verdict have the right to express their opinions; I just ask that they do so in a peaceful manner," Fallin said in a statement. "I appeal to Tulsans and others to remain calm."

The nine-person jury took about nine hours to deliberate. The trial, which lasted eight days, focused on whether Shelby was justified in using deadly force against Crutcher, or if her actions were based on fear.

Shelby testified for more than two hours on Monday about her training as a Tulsa police officer and how she believed Crutcher was reaching for a gun inside his SUV when she fired, according to ABC’s Tulsa affiliate KTUL.

The NAACP Legal Defense and Educational Fund, a civil and human rights law organization, said it was "deeply disappointed" by the verdict. The organization said it is now awaiting the result of a separate Department of Justice probe.

"We are deeply disappointed that yet another police officer has eluded conviction for killing an unarmed African American," NAACP LDEF President Sherrilyn Ifill said in a statement Wednesday. "We eagerly await the findings of the Department of Justice's investigation, and hope that federal charges will be filed given the egregious misconduct."

The shooting was among a string of highly publicized officer-involved shooting deaths of African American across the U.S. in recent years.

Terrence Crutcher's sister, Tiffany Crutcher, told reporters after the verdict came in that her brother never attacked or threatened Shelby, who said she feared for her life during the roadside encounter.

"Betty Shelby murdered my brother and after she murdered my brother the Tulsa police department covered up for her," she said.

Terence Crutcher's father, Rev. Joey Crutcher echoed her remarks in a statement after the announcement.

"Let it be known that I believe in my heart that Betty Shelby got away with murder," he said.

Tulsa County District Attorney Steve Kunzweiler commended the jury for their service, and noted that the case was a difficult one.

"I commend these jurors for their courage to step into a courtroom," he said. "It was, is and will continue to be a difficult issue to discuss for my community."

"There can be no doubt that the decision rendered by this jury was only after a long and deliberative process," Kunzweiler added.

ABC News' Clayton Sandell and The Associated Press contributed to this report.