SANFORD, Florida (CNN) — Special prosecutor Angela Corey has decided against using a grand jury in the case involving the shooting death of 17-year-old Trayvon Martin, her office said Monday.

The grand jury, set to convene Tuesday, was “previously scheduled by the former prosecutor,” said the statement from Corey.

“The decision should not be considered a factor in the final determination of the case,” her office said.

Corey said the investigation into the case continues. The state attorney has maintained that a grand jury is not needed to file possible criminal charges against George Zimmerman, the neighborhood watch volunteer who killed the teen February 26.

The case has triggered a nationwide debate about Florida’s “stand your ground” law — which allows people to use deadly force anywhere they feel a reasonable threat of death or serious injury — and race in America.

Thousands have converged on Sanford to join in protests calling for Zimmerman’s arrest and criticize the police department’s handling of the case.

On Monday, a group of students calling themselves the Dream Defenders marched to the Sanford police station, singing and carrying a banner saying, “We are Trayvon Martin.” The march began Friday in Daytona Beach, about 40 miles away, and continued through the weekend.

The marchers linked arms, sang and chanted as they faced the building’s entrance Monday. Six of the demonstrators, wearing hoodies, were blocking the department’s main entrance. Martin was wearing a hoodie when he was killed.

The Sanford Police Department said in a statement its office was “temporarily closed to the public … due to the actions of student protestors. The students are currently occupying the space in front of the police department blocking the main entrance.” The protest will not affect police and fire response to emergency calls, the department said.

“The city of Sanford hopes the actions of the students will be as peaceful and orderly as the previous rallies and marches have been,” City Manager Norton Bonaparte Jr. said.

Two prosecutors are working to determine whether there is sufficient evidence to bring charges against Zimmerman, 28.

Corey said previously she has never used a grand jury to decide on charges in a justifiable homicide case.

“We do a thorough investigation. We make that decision ourselves,” she said.

It is unknown whether prosecutors have interviewed Zimmerman. In late March, Corey told CNN sister network HLN that prosecutors had yet to speak to him, nor did her office know where he was.

Zimmerman’s attorneys say he is available anytime to talk to the special prosecutor.

Prosecutors are trying to unravel what happened the night that Martin was killed. Witnesses and attorneys for both sides have offered conflicting accounts.

What is known is that Martin ventured out from his father’s fiancee’s home in Sanford to get a snack at a nearby convenience store. As he walked home with a bag of Skittles and an Arizona iced tea, he was shot and killed by Zimmerman.

Sanford police questioned Zimmerman and released him without charges.

From there, the case has evolved into opposing allegations from Zimmerman’s supporters, Martin’s family and authorities.

Zimmerman says he killed Martin in self-defense after the teen punched him and slammed his head on the sidewalk, according to an Orlando Sentinel report that was later confirmed by Sanford police.

One of the responding officers saw a wound on the back of Zimmerman’s head and a bloody nose, and noted that his back was wet — indicating he had been lying in the grass, according to the police report.

An enhanced copy of a surveillance video showing him in police custody after the shooting appears to show a bump, mark or injury on his head.

Martin’s family and supporters have dismissed the video.

They say Zimmerman, who is Hispanic, racially profiled the teen, who was black, and ignored a police dispatcher’s directive not to follow him.

Zimmerman’s attorneys interpret the call differently, and say the operator did not order Zimmerman not to follow Martin.

A recording of a 911 call made the night of the shooting captured someone pleading for help. Zimmerman has said he was yelling for help, according to his family members and his account to authorities.

Martin’s relatives have said they are certain the voice calling for help on the 911 call is Martin’s.

Audio experts Tom Owen and Ed Primeau, who analyzed the recordings for the Orlando Sentinel using different techniques, said they don’t believe the voice is Zimmerman’s.

They compared the screams with Zimmerman’s voice, as recorded in a 911 call he made minutes earlier describing a “suspicious” black male.

The debate was further muddied when a witness, who declined to be identified by CNN, said she saw and heard the incident through her window.

When pressed on whether she could determine who was yelling, the witness said, “It was the younger, youthful voice (rather) than it was the deep voice I heard when they were arguing.”

Zimmerman’s attorneys have questioned the account, saying it was dark at the time of the shooting.

Until now, only friends and relatives of Zimmerman’s have come forward to speak on his behalf. Zimmerman’s attorneys have said he wants to share his story but can’t because of threats to his safety and the possibility of charges.

Martin’s family has said a Sanford police detective filed an affidavit saying he did not find Zimmerman’s statements after the shooting credible — but that Sanford Police Chief Bill Lee and State Attorney Norm Wolfinger met the night of the shooting and disregarded the detective’s advice.

Neither police nor prosecutors have confirmed the existence of such an affidavit. And Wolfinger has vehemently denied that such a meeting occurred.

The two sides have also debated what Zimmerman whispered under his breath during his 911 call.

Martin’s supporters said he uttered a racial slur; Zimmerman’s lawyer said he told them he whispered “punks.”

“We don’t know” whether a grand jury will choose to indict, said Zimmerman’s attorney, Craig Sonner.

Gov. Rick Scott appointed Corey as a special prosecutor as calls for “Justice for Trayvon” grew in the days following the shooting.

Authorities have said Zimmerman was not immediately charged because there were no grounds, at the outset, to disprove his account that he’d acted to protect himself.

The governor has formed a task force to review the “stand your ground” law.

— CNN’s Eric Fiegel, Martin Savidge and Ashleigh Banfield contributed to this report.