(CNN) -- His GPS monitor has been cut off and George Zimmerman is free -- but only legally.
Zimmerman fears for his life. He's a reviled figure to millions, despite his acquittal Saturday night in Trayvon Martin's killing. And he could still be held criminally liable for Martin's death.
'They want revenge'
Zimmerman's attorney describes him as a marked man.
"He has to be very cautious and protective of his safety because there is still a fringe element who have said ... that they will not listen to a verdict of not guilty," said Mark O'Mara.
Zimmerman, 29, has kept his address under wraps for more than a year and worn a disguise whenever he left his four walls. He has often strapped on body armor, according to O'Mara.
And he may feel the need to be armed.
When asked by CNN's Piers Morgan whether Zimmerman will keep the gun used in the killing, his brother, Robert Zimmerman Jr., said, "I don't see any reason why he shouldn't.
"I think he has more reason now than ever to think that people are trying to kill him because they express they're trying to kill him, all the time, every day, on my Twitter feed, on the Internet."
Robert Zimmerman gave more details Sunday on CNN's "New Day."
"The threats are vile, they're vicious, they're disgusting. And sometimes they're in person. People wearing shirts with my brother's face on it in crosshairs, encouraging others to act out violently against him. I know that you can't take every one one of those seriously, but you can't afford to be wrong either. Because you can be dead wrong if somebody really were intent on harming you."
"He's going to have to learn to move about in a very low-profile way and keep to himself," Robert Zimmerman said, although having the GPS removed and no trial to occupy his days helps end George Zimmerman's feeling of being "kind of caged in."
Zimmerman, married with no children, may leave Florida and choose to lead a life in the shadows -- like Casey Anthony, the Florida woman acquitted of killing her 2-year-old daughter in 2008.
Zimmerman could face more criminal charges
With the state criminal case over, George Zimmerman could now face new criminal charges.
The federal government could file a civil rights suit, accusing him of violating 17-year-old Martin's civil rights.
The NAACP has called on the Justice Department to file civil rights charges, and is asking the public to sign a petition.
"The most fundamental of civil rights -- the right to life -- was violated the night George Zimmerman stalked and then took the life of Trayvon Martin," the group said.
Zimmerman, a neighborhood watch volunteer, acknowledged killing the unarmed teen, saying it was in self-defense.
The Justice Department did not respond directly to the NAACP demand. It has a separate federal investigation going on.
An official told CNN the department "continues to evaluate the evidence generated during the federal investigation, as well as the evidence and testimony from the state trial."
Meanwhile, the Martin family could file a civil lawsuit against Zimmerman, seeking damages. The suit would claim wrongful death -- which is easier to prove than murder or manslaughter.
And the Rev. Al Sharpton said the acquittal was "only the first round in the pursuit of justice."
NAACP President Ben Jealous expects legal action will proceed on both fronts.
"There will be a civil phase almost assuredly, and then there will be a federal civil rights phase," he told CNN's "State of the Union" on Sunday. "And we are putting our faith in that system."
Robert Zimmerman rejected Jealous' call for charges against his brother. Authorities have interviewed "about three dozen of his closest friends and acquaintances. And there is not any inkling of racism,"he said. "In fact, there's evidence to show the opposite. I would encourage them to cool their jets, give everyone some time to kind of process what's going on.
"Agitation doesn't help us. It doesn't do anybody any good right now."
'Emotional and psychological hurdles'
Those who defend Zimmerman say he will struggle for the rest of his life over what happened, despite his contention that it was in self-defense.
"In his religious beliefs, death by any definition is a tragedy," Robert Zimmerman told CNN's Piers Morgan. "So he has moral things that he's going to have to deal with, and emotional and psychological hurdles he's going to have to overcome."
Those who believe he should be in jail for murder are quick to point out that Martin lost his life, and say there should be no tears shed for any struggles Zimmerman may face.
A young man's post on Facebook about Zimmerman's future quickly went viral Sunday.
"For the rest of your life you are now going to feel what its like to be a black man in America," Alex Fraser wrote.
"You will feel people stare at you. Judging you for what you think are unfair reasons. You will lose out on getting jobs for something you feel is outside of your control. You will believe yourself to be an upstanding citizen and wonder why people choose to not see that. ...
"I bet you never thought that by shooting a black male you'd end up inheriting all of his struggles."
Fraser added, "Enjoy your 'freedom.'"
Support for Zimmerman
Zimmerman's supporters have sent letters and e-mails to his lawyers, offering moral support and saying they sympathized with a man so concerned about neighborhood break-ins that he bought a gun and dog, and donned the mantle of neighborhood watchman.
The letters often blame the media for his woes and offer encouragement for the road ahead.
After the verdict, O'Mara too assailed news outlets for their coverage.
"He was like a patient in an operating table where mad scientists were committing experiments on him and he had no anesthesia," he said.
Many supporters sent in money to a website he established to help with his mounting legal bills.
But one crisis public relations manager said Zimmerman must tread lightly when accepting further public money.
"He's got to be careful about who he associates with afterward, even if they are offering financial support," said Gene Grabowski.
Despite what may lie ahead, on Saturday night, as his legal team surrounded him and congratulated each other with handshakes and hugs, George Zimmerman seemed to take a moment to soak in the relief -- aware that a long road lies ahead.
CNN's Michael Martinez contributed to this report.