A grand jury in St. Louis has reached a decision on whether or not to indict Darren Wilson, the white police officer who shot unarmed black teen Michael Brown last summer. It is expected to be announced at 9 p.m. EST Monday evening.

Michael Brown Sr., the teen's father, confirmed a decision had been reached to CBS News. However, Brown Sr. said he was not informed of what the decision will be.

"I'm just trying to stay strong, that's all," Brown Sr. said, in an interview that can be seen in the video above.

Get Breaking News Delivered to Your Inbox

The late teen's father said he hopes the protesters supporting his son "stay positive" in reaction to whatever the grand jury decides, and that they remain peaceful.

Brown's family plans to issue a statement Monday night, after the decision is announced, and give a press conference Tuesday morning at Greater St. Mark Church.

At a press conference Monday evening, before the decision was announced, Missouri Gov. Jay Nixon called for "peace, respect and restraint."

"No matter what is announced, people will be emotional," St. Louis County Executive Charlie Dooley said. "This is not the time to turn on each other, its time to turn to each other."

"What happened to Michael Brown has deeply divided us," St. Louis Mayor Francis Slay said. "Over the next few days, we expect to see St. Louisans loudly, passionately expressing their views. My message to the protesters: We will protect your right to peacefully assemble and speak your mind." But Slay warned demonstrators, "turning violent will not be tolerated."

Protests are expected Monday night at the and at the Ferguson Police Department. The group Ferguson Action is also planning demonstrations for 7 a.m Tuesday at Shaw Park in Clayton and at noon at Keiner Plaza in Ferguson.

Prior to the announcement, demonstrators had gathered outside the Ferguson Police Department.

Ferguson PD HQ pic.twitter.com/Agk2mdC4BG — Jake Barlow (@PhotoBarlow) November 25, 2014

National Guard troops were taking up positions at the Buzz Westfall Justice Center in Clayton, Mo., where the decision was going to be announced.

Waiting to enter courtroom where Darren Wilson GJ decision will be read. Nat'l guard standing by. #Ferguson pic.twitter.com/UHTTyJihlT — Jonathan Blakely (@JonathanBlakely) November 25, 2014

Demonstrations were taking place in other cities around the U.S., including New York, Philadelphia, Oakland and Los Angeles.

Schools in the Ferguson-Florissant School District will be closed Tuesday. Other local communities have also cancelled classes for Tuesday.

The August 9 shooting death of 18-year-old Brown, who was black and unarmed, by Darren Wilson, a white police officer, unleashed a flurry of protests in Ferguson. The initial demonstrations triggered a forceful police response that drew criticism from both local residents and the governor of Missouri.

The disputed circumstances surrounding the death also brought global notoriety to the St. Louis suburb, where the majority of the population is black but the police force is predominantly white. The grand jury's decision was being closely watched across the U.S., especially in cities where police relations with minority communities have been contentious.

On Monday, Gov. Jay Nixon declared a state of emergency, saying the National Guard would be deployed to assist police if necessary. Earlier this month, Brown's parents called on their son's supporters as well as law enforcement to remain "peaceful, calm and dignified."

Wilson, who is on paid administrative leave, has remained in seclusion throughout the investigation.

The St. Louis Post-Dispatch recently published new audio recordings of police radio communication before and after the shooting that showed that the encounter between Wilson and Brown took less than 90 seconds. However, the audio failed to answer many crucial questions about what actually happened.

In the recordings, a dispatcher can be heard reporting a "stealing in progress" and a physical description of the suspect, who was believed to have stolen cigars. Officers were told the suspect was running from a convenience store with a second man. Ferguson police subsequently released surveillance video of the convenience store theft, identifying Brown as the suspect.

Wilson asked the officers searching for the robbery suspects if they needed assistance. An officer responded that the men had disappeared. Two minutes later, Wilson radioed in: "Put me on Canfield with two. And send me another car."

Wilson reportedly told investigators that he instructed Brown and his friend Dorian Johnson to stop walking in the street. Wilson said he then recognized that Brown matched the suspect's description, called for backup and stopped his SUV next to the two men.

What happened next remains unclear.

Wilson said Brown attacked him. Some witnesses have said Wilson and Brown struggled, either outside or inside the officer's SUV. Others said they saw Brown with his hands over his head, getting on the ground.

At the end of the audio, an unidentified officer says: "Get us several more units over here. There's gonna be a problem." A woman can be heard crying in the background.

Brown was pronounced dead at the scene.

The St. Louis Post-Dispatch also released video that showed Wilson leaving a St. Louis-area hospital shortly after the shooting. In the video, Wilson appears to be uninjured - even though police originally reported that the officer had suffered an orbital eye socket "blowout."

"We don't see him holding his eye anywhere in that video," said Brown family attorney Benjamin Crump, who added that "it would appear the initial descriptions of his injuries were exaggerated."

The Justice Department is investigating the Ferguson Police Department for possible civil rights violations, including whether officers there use excessive force and engage in discriminatory practices. Last month, a source told CBS News that Attorney General Eric Holder was "exasperated" by what he called "selective leaks" - which appeared to support Wilson - in the case.

The New York Times reported that Wilson told investigators he "feared for his life" after Brown tried to grab his gun. An official autopsy report published by the St. Louis Post-Dispatch showed that Brown had been shot at close range, and that Brown had marijuana in his system when he died.

On August 25, thousands gathered in St. Louis for Brown's funeral, where the teenager was remembered as a "gentle soul" with ambitions that one day "the world would know his name."