Protesters are expected to gather Saturday at Freedom Plaza in memory of Trayvon Martin, whose death at the hands of a neighborhood watch volunteer has stirred the passions of the nation.

Martin, a black Florida teenager, was fatally shot last month as he walked back from a convenience store toward a home in a gated community.

George Zimmerman, who is Hispanic, said he killed Martin in self-defense. No charges have been filed against him. Martin, who was unarmed, held a bag of Skittles and a can of iced tea in his hands.

The death of the 17-year-old has launched a federal investigation and fueled calls for justice.

On Friday, President Obama weighed in on the incident, describing it as a “tragedy.”

“If I had a son, he’d look like Trayvon,” Obama said from the Rose Garden. “When I think about this boy, I think about my own kids.”

Obama did not address the local law enforcement’s effort or call for Zimmerman’s arrest. Instead, he directed his comments to Martin’s parents, saying they “are right to expect that all of us, as Americans, are going to treat this with the seriousness it deserves.”

Saturday’s rally, from 2 to 4 p.m. at Freedom Plaza, will be one of many that have taken place.

From California to New York, demonstrators have called for charges to be filed against Zimmerman.

On Wednesday, the “Million Hoodies March” was held in New York City, where hundreds in support of Martin covered their heads in hoodies. Martin was wearing a hoodie when Zimmerman, 28, followed him through the gated community and told a 911 operator that the teenager looked suspicious. The 911 operator directed Zimmerman not to pursue the teen.

Organizers of Saturday’s rally have asked demonstrators to wear black or hoodies.

Millions of others have taken to social media, posting pictures of themselves on Facebook wearing hoodies asking “Do I look suspicious?” and adding pictures of Martin to their Twitter and Facebook pages.