JACKSONVILLE, Florida — Prosecutors Wednesday charged a neighborhood watch guard with second-degree murder in the killing of an unarmed US black teenager that sparked nationwide anger amid suspicions it was racially motivated.

"Today, we filed an information charging George Zimmerman with murder in the second degree," Florida state attorney general Angela Corey told a press conference.

"I can tell you, we did not come to this decision lightly," she added after a weeks-long investigation into the February death of 17-year-old Trayvon Martin.

Zimmerman, who is Hispanic, is accused in the fatal shooting of Martin during an altercation inside a gated community in the central Florida town of Sanford.

Corey also confirmed that Zimmerman, who had gone underground, was now in custody in Florida and would appear in front of a judge at an appropriate time.

Zimmerman's supporters say Martin attacked first, breaking Zimmerman's nose before knocking him to the ground and repeatedly slamming his head against the sidewalk. They insist Zimmerman fired in self-defense.

But Martin's family and supporters say the teenager may have been the victim of racial profiling.

A controversial Florida law allows the use of deadly force when a person senses a reasonable fear of death or serious injury.

Corey, who was appointed special prosecutor in the case, acknowledged the pressure that her department had been under, saying "we do not prosecute by public pressure or petition. We prosecute based on the facts of any given case as well as the laws of the state of Florida."

"We are not only ministers of justice, we are seekers of the truth," she added.

Speaking at a Washington press conference organized by the National Action Convention earlier in the day, Martin's mother, Sybrina Fulton, and father, Tracy Martin, said they had faith in the justice system.

The parents also shared stories of their pain since their son's death as they have fought for justice, launching a global petition that has collected more than 2.5 million signatures.

"It's been a nightmare for the past 44 days," said Fulton, her voice quivering as she struggled to hold back the tears. "I've been up and down like a rollercoaster. But I know that justice will be served."

"As a parent who loses their child," said Tracy Martin, "it's very difficult to maintain our sanity."

Martin said he had been touched by the outpouring of support the family has received. To honor his late son's legacy he said he would, among other things, "teach our kids conflict resolution."

Fulton added: "By God's grace I'm here. If not I'd be holed up in my room crying."

Federal investigators are also continuing a three-week probe of the case.

"If we find evidence of a potential federal criminal civil rights crime, we will take appropriate action," US Attorney General Eric Holder said earlier at the National Action event.

Holder said senior Justice Department officials traveled to Sanford to meet with the Martin family and local residents and authorities.

"In all of these discussions, we're listening carefully to concerns -- and emphasizing that the department will conduct a thorough and independent review of the evidence," Holder said.