JACKSONVILLE, Fla. — The neighborhood watch volunteer who shot 17-year-old Trayvon Martin was arrested and charged with second-degree murder Wednesday after weeks of mounting tensions and protests across the U.S.

George Zimmerman, 28, could get up to life in prison if convicted in the slaying of the unarmed black teenager.

Special prosecutor Angela Corey announced the charges but would not discuss how she arrived at them or disclose other details of her investigation, saying: “That’s why we try cases in a courtroom.”

Second-degree murder is typically brought in cases when there is a fight or other confrontation that results in death but involves no premeditation to kill. It carries a mandatory minimum of 25 years behind bars when a gun is used.

Martin’s parents expressed relief over the decision to prosecute their son’s killer.

“The question I would really like to ask him is, if he could look into Trayvon’s eyes and see how innocent he was, would he have then pulled the trigger? Or would he have just let him go on home?” said his father, Tracy Martin.

Corey would not disclose Zimmerman’s whereabouts for his safety but said that he will be in court within 24 hours, at which point he can request bail. He turned himself in in Florida.

Zimmerman’s new attorney, Mark O’Mara, said Zimmerman will plead not guilty and will invoke Florida’s “stand your ground” law, which gives people wide leeway to use deadly force without having to retreat in the face of danger. The lawyer asked that people not jump to conclusions about his client’s guilt and said he is “hoping that the community will calm down” now that charges have been filed.

“I’m expecting a lot of work and hopefully justice in the end,” O’Mara said.

On Tuesday, Zimmerman’s former lawyers portrayed him as erratic and in precarious mental condition. But O’Mara said Zimmerman was OK: “I’m not concerned about his mental well-being.”

Zimmerman, whose father is white and whose mother is Hispanic, has asserted since the Feb. 26 killing in Sanford that he shot in self-defense after the teenager attacked him. Martin’s family argued Zimmerman was the aggressor.

The shooting brought demands from black leaders for his arrest, touched off protests in which people wore hooded sweatshirts like the one the teenager had on, and set off a furious debate over race and self-defense that reached all the way to the White House, where President Barack Obama observed: “If I had a son, he’d look like Trayvon.”

Separately, the U.S. Justice Department’s civil rights division is conducting its own investigation.

Corey said the decision to bring charges was based on the facts and the law, declaring: “We do not prosecute by public pressure or by petition.”

One of the biggest hurdles to Zimmerman’s arrest over the past month was Florida’s “stand your ground” law, which affords strong protection to those who use deadly force.

Second-degree murder means a killing that was not premeditated but resulted instead from an “imminently dangerous act” that showed a “depraved” lack of regard for human life.

Some legal experts had predicted the prosecutor would instead bring a charge of manslaughter, which carries up to 15 years behind bars. It is defined as a death that results from a reckless but not a depraved act.

Corey repeatedly declined to answer questions about details in the case.

“So much information got released on this case that never should have been released. We have to protect this prosecution and this investigation for Trayvon, for George Zimmerman,” she said.

Legal experts said Corey must have compelling evidence against Zimmerman if she chose to charge him with second-degree murder.

“That indicates they have evidence (Zimmerman) was chasing Trayvon because he was black,” said Florida defense attorney Richard Hornsby. “It’s difficult to think how one prosecutor didn’t charge him at all and another thought there was enough evidence to justify a second-degree charge. It’s a pretty drastic swing.”

Tensions have risen in recent days in Sanford, a town of 50,000 outside Orlando. Someone shot up an unoccupied police car Tuesday as it sat outside the neighborhood where Martin was killed. And a demonstration by college students closed the town’s police station Monday.

But as the hour of the prosecutor’s announcement neared, the Martin family and their lawyer pleaded for calm.

Outside Sanford City Hall, Stacy Davis, a black woman, said she was glad to see arrested Zimmerman under arrest. “It’s not a black or white thing for me. It’s a right or wrong thing. He needed to be arrested,” she said. “I’m happy because maybe that boy can get some rest.”

Six weeks ago, Martin was returning to the home of his father’s fiancee from a convenience store with Skittles candy and ice tea when Zimmerman, the neighborhood crime-watch captain in the gated townhouse community, started following him.

Zimmerman told police dispatchers: “This guy looks like he is up to no good — he is on drugs or something.” The 911 dispatcher told him not to follow the young man.

At some point, the two got into a fight and Zimmerman used his gun.

Zimmerman told police Martin attacked him after he had given up chasing the teenager and was returning to his truck. He told detectives that Martin knocked him to the ground and began slamming his head on the sidewalk. Zimmerman’s father said his son suffered a broken nose.

Amid the uproar of the failure to arrest Zimmerman, the local prosecutor disqualified himself from the case, and Gov. Rick Scott appointed Corey, the prosecutor for Jacksonville, to take it over.

Corey has tried hundreds of homicide cases and is known for hardball tactics and her passionate devotion to victims’ rights. She said she met with Martin’s “sweet parents” and prayed with them.

“We only know one category as prosecutors, and that’s a ‘V,'” she said at the news conference, referring to victims, and making a V with her fingers.