George Zimmerman was taken into police custody after being charged Wednesday evening with second-degree murder in the Feb. 26 shooting death of 17-year-old Trayvon Martin, a Florida special prosecutor said.

Angela Corey, who was appointed by Gov. Rick Scott to re-examine the highly publicized case after police released Zimmerman soon after the shooting, told a packed news conference that she had sought the most severe charge possible. Because Corey previously said she wouldn't be presenting the case to a grand jury, a charge of first-degree murder wasn't an option.

Zimmerman, 28, could face life in prison if convicted.

I can tell you we did not come to this decision lightly, Corey said at her office in Jacksonville, Fla. 

She stressed that the charge wasn't the result of intense publicity or public anger over Martin's killing, which has prompted rallies across the United States and a 2 million-signature petition campaign for Zimmerman's arrest.

We do not prosecute by public pressure or by petition, said Corey, who was appointed to the case less than three weeks ago.

Corey said she and her team, with help from the police department in Sanford -- the Orlando suburb where Zimmerman, a neighborhood-watch volunteer, admits killing Martin -- examined evidence in the case as part of a never-ending quest for truth.

Sanford police have been publicly maligned over their handling of the crime, which took place in a gated community where Martin was staying with his father and his father's fiancee. The high school student was walking back in the rain from a convenience store when Zimmerman saw him and called 911. He followed Martin even after a police dispatcher told him not to, and the two got into a struggle.

Zimmerman told police the unarmed Martin had punched him in the nose, knocking him to the ground, and then began banging the man's head on the sidewalk. Police took Zimmerman into custody the night of the shooting but released him without charges.

On Wednesday, Zimmerman turned himself in to police and was arrested on a previously issued court warrant. Corey didn't specify where the accused was being held, citing concern for his safety, but hours later Zimmerman -- his head covered -- was ushered out of a black SUV and into the jail in Florida's Seminole County, the Orlando Sentinel reported.

Zimmerman's new lawyer, Mark O'Mara, said his client would make his first court appearance Thursday and plead not guilty. Corey told the news conference that Zimmerman was being held without bond, but O'Mara said he would ask the judge at Thursday's court proceeding to set a bond allowing for his client's release, MSNBC reported.

I think he's troubled by the fact the state decided to charge him, O'Mara said of Zimmerman. I would think anyone charged with second-degree murder would be scared.

Martin's parents said they were satisfied with the charges, 

We just wanted an arrest and we got it. Thank you, God; thank you, Jesus, the teen's mother, Sybrina Fulton, was quoted as saying.  

This case will turn in large part on the question of whether the shooting fell under Florida's stand your ground law, which gives a person leeway to use deadly force rather than retreat during a fight if he believes his life is in danger. Those who claim to have acted in self-defense under the law aren't legally required to prove they truly feared for their safety.

During her news conference, Corey acknowledged that self-defense could pose some challenges if Zimmerman's lawyers use it as a defense in the criminal case. But she said that if 'stand your ground' becomes an issue, we will fight it.

Zimmerman told authorities the night of the killing -- and has maintained since -- that he shot Martin in self-defense after the teenager punched him in the face and tried to take his gun. Critics have challenged that version of events, saying the crime appears to have been racially motivated given Zimmerman's description in his call to 911 that Martin looked suspicious and up to no good.

Martin was black; Zimmerman is the son of a white father and Hispanic mother.

Following Wednesday's news conference, civil-rights activist Al Sharpton appeared with Martin's family and their lawyer to respond to the prosecutor's announcement. Sharpton, who has helped lead rallies calling for Zimmerman's arrest, praised the Florida government -- and Scott, its Republican governor, in particular -- for taking steps toward justice for the victim and his family.

Tonight, maybe Americans can come together and say only the facts matter when you're dealing with a loss of life, Sharpton said, before adding that Zimmerman's arrest and incarceration isn't an event to be celebrated.

He deserves a fair trial. This isn't about gloating, it's about pursuing justice, he said.

In response to Wednesday's events, Martin's parents thanked people across the country who had expressed support and demanded justice in the case.

We simply wanted an arrest, Fulton said tearfully. I just want to speak from my heart to your heart, because a heart has no color. I want to thank you.