Police chief steps down after Trayvon Martin shooting

Demanding justice in the Trayvon Martin shooting, buses filled with agitators descended on Sanford, Florida, on Thursday as pressure mounted for police to arrest George Zimmerman, the man who shot the 17-year-old boy walking in his neighborhood.

Sanford Police Chief Bill Lee stepped down Thursday after calls for his ouster intensified. “I have come to the position that I must temporarily remove myself as the police chief of Sanford,” he said. "I do this to restore some semblance of calm to the city which has been in turmoil for several weeks,” he said.

Meanwhile in the embattled city of nearly 20,000 residents, an evening rally planned for a small Sanford church, First Shiloh Missionary Baptist, was moved to a local park in the wake of an influx of people coming to town. CNN reporters on the ground described people milling around with "I Am Trayvon Martin" posters and wearing hoodies, a reference to the teenager's attire on the night he was killed.

Buses were arriving from around the country. In Atlanta, CBS radio host and former city councilman Derrick Boazman led a group of buses to Sanford to show support for the rally. The Rev. Al Sharpton, whose mother died in the early morning, led the Sanford rally, which drew a large crowd of supporters.

The developments came one day after throngs of people crowded New York streets in a "Million Hoodie March." On social networking sites, people donned hoodies and uploaded pictures of themselves, including former Michigan Gov. Jennifer Granholm.

“Every mother knows their child. And that’s his voice,” a sobbing Sybrina Fulton, the boy's mother, told CNN’s Anderson Cooper Wednesday night.

Referencing audio tapes of 911 calls after the shooting the boy's father, Tracy Morgan said: “He saw his death coming. The screams got more frantic and at that second that we heard the shot the screams just completely stopped. He was pleading for his life."

George Zimmerman has said he shot the teenager, but argues it was self-defense.

Students rally

On Thursday, students at Miami’s Carrol City High School staged a walkout in support of Martin, whose death while walking in a gated community has galvanized much of the nation against what they see as an inept police response. Miami-Dade law enforcement police on motorcycles and in cruisers were trailing the students and blocked streets for them, according to HLN affiliate WVSN in Miami.

The February shooting of Martin has attracted the attention across the nation and in parts of the world and has brought new scrutiny to Florida's "Stand Your Ground" law which critics feel stretches the boundaries of self-defense.

Maryland Democrat Rep. Steny H. Hoyer released the a statement Thursday commending federal officials for launching in investigation into the shooting.

“Americans from all walks of life are rightly appalled by his tragic death. Trayvon deserves justice, and his family and his community deserve answers. It is my hope that the Justice Department’s investigation will provide those answers and that appropriate action will be taken to punish any wrongdoing to the fullest extent of the law,” Hoyer said.

Federal prosecutors, the FBI and a Florida grand jury have all announced investigations in the incident.

Zimmerman has not been arrested. A police report calls him a white male; his family says he is Hispanic and that he has wrongly been described as a racist.

The uproar over Martin's death has reverberated nationwide with demands for Zimmerman's arrest and scrutiny of police actions.