(CNN) -- Florida neighborhood watch volunteer George Zimmerman has been charged with second-degree murder in the death of 17-year-old Trayvon Martin and is in custody, a special prosecutor announced Wednesday.

Zimmerman, 28, was arrested on a warrant and was in the custody of the Florida Department of Law Enforcement, his new attorney, Mark O'Mara, told CNN legal analyst Mark NeJame.

He said his client will enter a plea of not guilty.

In Florida, a conviction for second-degree murder carries a maximum sentence of life in prison.
Although details of the evening shooting remain murky, what is known is that Martin, an African-American, ventured out from his father's fiancee's home in Sanford to get a snack at a nearby convenience store.

As he walked back with a bag of Skittles and an Arizona Iced Tea, he was shot and killed by Zimmerman, who is Hispanic. Zimmerman had called 911 to complain about a suspicious person in the neighborhood, according to authorities.

In the call, Zimmerman said he was following Martin after the teen started to run, after which the dispatcher told him, "We don't need you to do that." Zimmerman pursued Martin anyway, before saying he lost sight of him.

Authorities have said Zimmerman was not immediately charged because there were no grounds, at the outset, to disprove his account that he'd acted to protect himself. A police report indicated the volunteer was bleeding from the nose and the back of his head.