(RNS) Calls for legal action in the shooting death of Florida teenager Trayvon Martin are growing as preachers took to their pulpits Sunday wearing “hoodies” in symbolic solidarity around the country.

One month after the death of the unarmed 17-year-old African-American by a neighborhood watch volunteer in Sanford, Fla., Jesse Jackson said the youth was a “martyr” whose death could be an opportunity to revive concerns about civil rights and violence. He called for a change in Florida's “Stand Your Ground” self-defense law, similar to one in more than 20 other states, that may have prevented charges from being filed in the case.

“How do we turn pain into power?” Jackson asked a standing-room only congregation while preaching at Macedonia Missionary Baptist Church in Eatonville, Fla., about 20 miles from the site of the Sanford shooting. “How do we go from a moment to a movement that curries favor?”

“The blood of the innocent has power,” Jackson said, naming other slain black Americans whose deaths became rallying cries in the struggle for equality. “There's power in the blood of Emmett Till. There's power in the blood of Medgar Evers. There's power in the blood of Dr. King.”

Concern over the killing was echoed in religious centers from Atlanta to New York and California, with many preachers and their congregations wearing hooded sweatshirts in Martin's memory.

Martin was wearing a hooded sweatshirt as he walked home on a rainy night in a gated community. The neighborhood watch volunteer who shot him, George Zimmerman, 28, has not been charged, and demands for an arrest in the slaying have been growing. The chief of the city's police force stepped aside last week amid criticism.

In Northern California, “Hoodie Sunday” was marked in hundreds of congregations including those in Oakland, Berkeley, San Jose and Sacramento, organizers said.

“As faith leaders, we are outraged that the killer showed so little regard for Trayvon that he took his life needlessly and senselessly,” the group, PICO, a network of faith-based community organizations, said in a statement. “We are outraged that local law enforcement officials have failed to act justly and expeditiously.”

Zimmerman had called police to report that a hooded figure in the neighborhood looked suspicious. Martin turned out to be carrying a bag of candy and a can of iced tea.

(William M. Welch writes for USA Today.)