Sanford Police Chief Bill Lee announced that he has temporarily stepped down as chief, during a press conference outside of Sanford City Hall on Thursday.

Civil rights leader Rev. Al Sharpton said he is coming to Central Florida to lead a rally for 17-year-old Trayvon Martin, who was shot and killed by neighborhood watch captain, George Zimmerman.

The rally for Martin has been moved to Fort Mellon Park from the First Shiloh Missionary Baptist Church on Thursday, due to an overwhelming response, according to a tweet from Al Sharpton.

Sharpton also said on Thursday, via Twitter, that he is on a flight to Florida for the rally at Fort Mellon Park in Sanford on East First Street, despite the death of his mother.

Sharpton's 87-year-old mother, Ada, died early Thursday. Sharpton said his mother would have wanted him to attend the rally.

Zimmerman claimed he acted in self-defense, and he hasn't been arrested. The lack of arrest in the case has prompted outrage from civil rights activists, local leaders and people from around the country.

The case is being reviewed by the State Attorney's Office.

• RELATED STORY: Hundreds march in NYC for Trayvon Martin
• READ: Sanford city manager's response to outcry

Martin's parents will meet with U.S. Justice Department officials before the rally. His parents, along with Sharpton will meet with the U.S. Attorney for the Middle District of Florida and the deputy assistant attorney general of the Civil Rights Division.

Sanford’s mayor said he is expecting as many as 20,000 people to gather at the park to rally for justice in the death of Martin.

However, an organizer of the event said he’s not expecting a crowd that large.

“We were anticipating initially that 2,000 people would roughly be in attendance,” said Dr. L. Ronald Durham.

Celia More attended a rally earlier in the week and plans to attend Thursday’s rally.church

“It could easily have gotten out of hand with something that's such a touchy subject. There are elderly people who are going to be there. There are children,” said More.

The rally is expected to draw people from around the country.

More than 200 people, including an Atlanta city council member, are on their way from a church in southeast Atlanta to attend.

WFTV has learned that local law enforcement agencies will be on hand to provide security for the event, but authorities won’t say which agencies will be involved.

Sanford Mayor Jeff Triplett said he is concerned about what could happen.

“There’s emails that walk the edge, and you hate to see it but you still have to take those things seriously,” said Triplett.

Downtown Sanford business owners said they have no plans to change operating hours because of the rally.

Theo Hollerbach, owner of the well-known Willow Tree Café, said his restaurant has 140 reservations for Thursday night and they had only 12 cancellations over fears about the rally.

He said he applauds the rally's efforts.

"It is people gathering for a good cause trying to make things right…I'm hoping they'll figure out a way to solve the issue," said Hollerbach.

The city is also preparing for another large event on Monday.

Sanford city officials said they have moved a planned town-hall-style meeting on Martin’s death from city hall to the city’s civic center, which can seat 600 people. They’ll provide outdoor seating for the event as well.

On Wednesday night, Commissioner Mark McCarty unexpectedly asked his fellow commissioners for a no confidence vote in Sanford Police Chief Bill Lee because of his handling of the investigation into the shooting.

"I don't see how he can continue," said McCarty.

"I am embarrassed because of this national shame," said City Commissioner Velma Williams.

While three of the five commissioners followed McCarty’s lead and cast the no confidence votes, it is City Manager Norton Bonaparte who will have the final say on Lee’s fate.

A number of residents in attendance cheered when the votes were cast.

The two commissioners who didn’t cast a vote of no confidence said they thought the vote was a knee-jerk reaction to the situation.

Rally Information:

• Seminole Boulevard between Mellonville and Sanford Avenue, and First Street between San Juan Avenue and Sanford Avenue downtown, will be closed from 12:00 p.m. until the ending of the rally.  The Rally is expected to last two hours.  The Florida Highway Patrol, Seminole County Sheriff’s Office, and the Department of Transportation will assist with traffic control.  Road signage will be on all major roadways.

• Parking for cars is available at City Hall, the Seminole County Court House, and on-street parking.  Parking is limited and persons should carpool.  Bus drop off will be at the Sanford Chamber of Commerce, 400 East First Street.