Sanford, Fla., police chief Bill Lee Jr. Thursday stepped down "temporarily" as the outcry mounted over the shooting of unarmed teenager Trayvon Martin.

The action came the same day rallies were held in numerous cities to protest the shooting of the 17-year-old black teenager and the police decision against arresting self-appointed neighborhood watch volunteer George Zimmerman.

Thousands gathered Thursday in Sanford's Fort Mellon Park, where the Rev. Al Sharpton, a civil rights activist and MSNBC personality, called for the arrest and prosecution of Zimmerman.

"Trayvon represents a reckless disregard for our lives," Sharpton said. "Enough is enough. Zimmerman should have been arrested that night."

Martin's mother, Sybrina Fulton, then addressed the rally, repeating a theme she has sounded in other appearances since her son's death.

"I stand before you today not knowing how I'm walking right now because my heart hurts for my son," she said. "Trayvon is my son. Trayvon is your son. Thanks so much for your support."

Sanford Mayor Jeff Triplett told the crowd he is committed to "find justice," the Orlando (Fla.) Sentinel reported.

In announcing he was stepping down temporarily, Lee said he hopes his action will "restore some semblance of calm," the newspaper reported.

"My role as the leader of this agency has become a distraction from the investigation," Lee said in a statement. "It is apparent that my involvement in this matter is overshadowing the process.

"Therefore, I have come to the decision that I must temporarily relieve myself from the position as police chief for the city of Sanford."

The city commission refused to give a vote of confidence to Lee Wednesday night; however, City Manager Norton Bonaparte told ABC News he would not decide on whether or not to dismiss Lee until the investigation into Martin's death was completed.

Martin was shot and killed Feb. 25 in a confrontation with Zimmerman, who said he fired in self-defense.

Lee has refused to arrest Zimmerman, who is white, incensing black residents and civil rights activists. The Rev. Al Sharpton flew in to lead a march through Sanford Thursday night.

Other marches were planned in cities including Pittsburgh; Chicago; Milwaukee; San Francisco; Oakland, Calif.; Washington; Norfolk, Va., and Iowa City, Iowa, a Facebook page reviewed by United Press International indicated.

In New York's Union Square Wednesday night, hundreds, including Martin's parents, took part in a "Million Hoodies March" in which many participants wore hooded sweatshirts as a symbol of solidarity. (c) UPI