March 18

Several hundred gather in Titusville for a rally at St. James AME Church, aiming to prod State Attorney Norm Wolfinger, whose office covers Seminole and Brevard counties, to file charges.

March 19

The Seminole County Sheriff's Office releases additional 911 calls made by Zimmerman in prior incidents. In four, he reports "suspicious" persons in or near the Retreat at Twin Lakes neighborhood.

Meanwhile, a source close to the investigation confirms to the Orlando Sentinel that the gun that killed Martin was fired only once on the night of the shooting, contradicting family attorneys' claims that Zimmerman fired a "warning shot."

March 20

A girl identified as Trayvon Martin's girlfriend speaks to ABC News. She says she was talking to the teen in the lead up to the shooting. Trayvon, she says, told her "some man was watching him." Later, she said she heard what sounded like Zimmerman pushing Trayvon.

At a rally in Sanford, the NAACP calls for the firing of Sanford Police Chief Bill Lee Jr. The rally was followed by a march to the Sanford Police Department.

State Attorney Norm Wolfinger's office announced a Seminole County grand jury will investigate the shooting, about 12 hours after the U.S. Department of Justice announced that it will review the case for any possible civil rights violations.

Rep. Corrine Brown and Sanford city leaders meet with U.S. Department of Justice representatives.

March 21

A Sentinel investigation reveals new details about Zimmerman's past, including money problems and issues involving domestic violence in a previous relationship.

That night, the Sanford City Commission votes "no confidence" in embattled police Chief Lee.

March 22

Lee steps down temporarily as police chief, explaining that his presence has become a "distraction." He announces the change at an afternoon press conference at Sanford City Hall.

Later, thousands gather at Sanford's Fort Mellon Park for a rally featuring the Rev. Al Sharpton, Martin Luther King III and other civil rights leaders and politicians attend and speak, calling for an arrest in the case.

Meanwhile, Gov. Rick Scott announces that a special prosecutor has been appointed to the investigation, replacing Brevard-Seminole State Attorney Norm Wolfinger.

March 23

President Barack Obama makes his first public comments on the controversy, declaring that "if I had a son, he'd look like Trayvon."

A Sentinel investigation reveals that Zimmerman was working as an underwriter at a Maitland mortgage risk-management firm before the shooting, and a new photograph of him surfaces. Meanwhile, the Washington Post reports new details of his religious upbringing.

Also, a Melbourne beach man is arrested, accused of sending threatening emails to Chief Lee. And Dateline NBC obtains a voicemail left by Zimmerman for a supportive neighbor, thanking him for his support.

March 24

Members of the New Black Panther Party announce a $10,000 reward for the "capture" of Zimmerman, the Neighborhood Watch volunteer who shot Trayvon Martin during a protest in Sanford.

March 25

The Rev. Jesse Jackson preaches before an estimated 1,600 people at the Macedonia Missionary Baptist Church in Eatonville. "If it's a moment, we go home," Jackson says. "If it's a movement, we go to war."

March 26

Police reveal new details of the investigation to the Sentinel about Zimmerman's version of the events of Feb. 26. Zimmerman, police say, was punched to the ground by Martin, and his head slammed into the sidewalk several times, leaving him bloody and battered.

Police say much of Zimmerman's account has been corroborated by witnesses.

Meanwhile, a rally is planned for 4 p.m. Baltimore evangelist the Rev. Jamal Bryant will hold a protest outside Sanford's City Hall. The protest will begin at First United Methodist Church, at 419 S. Park Ave., and end at the Sanford Civic Center.

At 5 p.m., a town hall meeting about Trayvon's death will be held at the Sanford Civic Center at 401 E. Seminole Blvd. The teenager's family will address those in attendance, and Jackson and Sharpton also are expected to attend.