(CNN) -- Here's a look at the timeline of events in the fatal shooting of Trayvon Martin in Sanford, Florida, and the ensuing uproar.
About 7 p.m.: George Zimmerman, a 28-year-old neighborhood watch captain, calls 911 to report "a suspicious person" in the gated community Retreat at Twin Lakes. Zimmerman says he is following Martin after the teen started to run, prompting the dispatcher to tell him, "We don't need you to do that." Zimmerman pursues Martin anyway, but then says he lost sight of him.
About 7:10 p.m.: Phone records show Martin was on the phone with his girlfriend around the time he saw Zimmerman while returning on foot from a convenience store to his the home of his father's fiancee.
At a March 20 news conference, Martin family attorney Benjamin Crump says the girl heard someone ask Martin what he was doing and Martin asking why the person was following him. The girl gets the impression that there is an altercation, during which the earpiece falls from Martin's ear and the connection goes dead, according to Crump.
According to an Orlando Sentinel story later confirmed by Sanford police, Zimmerman tells authorities that after Zimmerman briefly lost track of Martin, the teen approached him. After the two exchange words, Zimmerman says, he reaches for his cell phone, and then Martin punches him in the nose. Zimmerman says Martin pins him to the ground and begins slamming his head into the sidewalk.
About 7:25 p.m.: Martin is shot and killed. It is raining.
At the time of his death, the teenager is unarmed and carrying a small amount of cash, a bag of Skittles candy and a can of iced tea.
Several neighbors of the gated community call 911, with authorities eventually releasing the contents of seven such calls. In one, a man whispers, "Hurry, please. ... There's someone screaming outside. There's a gunshot. Hurry up. ... There's someone screaming. I just heard a gunshot."
Another neighbor says, "There were gunshots right outside my house. There's someone screaming. I just heard a guy shot. Hurry up. They are right outside my house."
In another call, a woman begs dispatchers to send help, saying someone is "screaming and hollering" for help. Moments later, she describes a light at the scene of the shooting. "Oh, my God," she says. "There's still somebody out there walking with a flashlight."
About 7:30 p.m.: Zimmerman tells police he shot Martin in self-defense. In a police report, Officer Timothy Smith writes that Zimmerman is bleeding from the nose and back of the head.
March 8: Trayvon Martin's father, Tracy Martin, family members and attorneys hold a news conference calling attention to the case.
March 12: Sanford Police Chief Bill Lee says Zimmerman has not been charged because there are no grounds to disprove his account of the events.
March 14: CNN's David Mattingly reports that police have concluded their investigation and turned the file over to the state attorney, who will decide whether to file charges. Martin's parents, Tracy Martin and Sybrina Fulton, create a petition on the website Change.org calling for Zimmerman's arrest. Within a week, it is the second most-popular petition in the website's history, with 877,110 signatures. The NAACP asks the Justice Department to get involved in the investigation.
March 15: In a letter to the Orlando Sentinel, George Zimmerman's father writes that his son has been unfairly portrayed as a racist. Robert Zimmerman writes that his son is Hispanic and grew up in a multiracial family.
March 16: Authorities release seven calls to police from the night of the shooting. In one of the 911 recordings, Zimmerman says he is following Martin. Also in one of the recordings, a voice can be heard in the background screaming "Help, help!" followed by the sound of a gunshot.
March 19: The Justice Department announces that it has launched an investigation into Martin's death. Florida Gov. Rick Scott asks state officials to assist in the investigation.
March 20: Florida Rep. Dennis Baxley, who sponsored the "stand your ground" law in 2005, says nothing in it allows people to "pursue and confront." The law allows people to use deadly force to defend themselves anywhere they feel a reasonable fear of death or serious injury. The Justice Department sends representation to Sanford to investigate and "to address tension in the community."
March 21: CNN analyzes one of the tapes of Zimmerman's call to dispatch, in which he is purported to have used a racial slur. The results are inconclusive.
March 22: Police Chief Lee announces that he is stepping down temporarily as head of the department, which has been criticized for its handling of the shooting. Scott announces that he is appointing State's Attorney Angela Corey of the 4th Judicial Circuit as special prosecutor, replacing Norman Wolfinger. As the petition calling for Zimmerman's arrest reaches 1 million signatures, according to Change.org, civil rights activists, politicians, family and supporters converge on Fort Mellon Park in Sanford to rally for swift judicial action, including Zimmerman's arrest.
March 23: President Barack Obama speaks publicly for the first time on the growing controversy, saying the incident requires national "soul-searching."
March 24: A handful of members from the New Black Panther Party offer a $10,000 reward for the "capture" of George Zimmerman.
March 26: One month after Martin was killed, demonstrators rally across the country calling for Zimmerman's arrest. In Sanford, the City Commission holds a town hall meeting on the incident and its aftermath.
March 28: Zimmerman's father, Robert, appears on television and says Martin threatened to kill Zimmerman and then beat him so badly that Zimmerman was forced to shoot.
March 29: Zimmerman's brother, Robert Zimmerman Jr., appears on CNN and says medical records will prove that his brother was attacked and his nose was broken by Martin before he fatally shot the teen.
March 29: A witness, who asks not to be identified, tells CNN of having heard voices, "opening a window and then seeing -- with two men or two people on the ground, one on top of each other" on the night Martin was shot dead.
March 31: Civil rights leaders join throngs of protesters carrying "Justice for Trayvon" signs on Saturday, marching to the Sanford, Florida, police headquarters to demand the arrest of Zimmerman.
April 2: Audio experts tell CNN that they don't believe it's Zimmerman who can be heard yelling "Help!" in the background of a 911 call. They compare those screams with Zimmerman's voice, as recorded in a 911 call he made minutes earlier describing a "suspicious" black male, who ended up being Martin.
April 5: Zimmerman says he whispered "punks," not a racial slur, in the moments before he shot Martin, his attorneys tell CNN. CNN's editorial staffers repeatedly review the tape but can reach no consensus on whether Zimmerman used a slur.
April 9: Special prosecutor Corey decides against using a grand jury in the case. "We believed, from day one, that they had enough evidence to arrest the killer of Trayvon Martin and now, as the evidence has continued to unfold, we think there has been a plethora of evidence to simply effect probable cause to do an arrest -- not for a conviction, but for an arrest," says family attorney Benjamin Crump.
April 10: Attorneys for Zimmerman say they have lost contact with their client and no longer represent him. Lawyer Hal Uhrig says Zimmerman has, on his own, called Sean Hannity of Fox News and the office of the special prosecutor appointed to lead the investigation. Uhrig also suggests that Zimmerman has left Florida.
Zimmerman's now-former lawyers and friend Frank Taaffe confirm the authenticity of a website as having been launched by the neighborhood watch volunteer to warn supporters about groups falsely claiming to be raising funds for his defense and to solicit donations for himself.
April 11: Zimmerman is charged with second-degree murder in the shooting death of Martin, says special prosecutor Angela Corey.
"This is a very, very major charge," says CNN Senior Legal Analyst Jeffrey Toobin. "It carries the potential of life in prison. The jury instructions that the jury will receive is he can only be convicted if he showed a depraved attitude toward Trayvon Martin's life. That's a tough burden for a prosecutor to meet. But she has access to facts that we don't."
April 12: An affidavit of probable cause in Florida's case against Zimmerman says he "profiled" Martin and disregarded a police dispatcher's request that he await the arrival of police. Zimmerman's relatives say that he did not profile Martin and that he shot him in self-defense. They say Zimmerman killed Martin after the teen punched him and slammed his head on the sidewalk.
April 18: A Florida judge approves a motion to disqualify herself from the case, according to the court. Zimmerman's defense team had requested that Seminole Circuit Judge Jessica Recksiedler, who was assigned to the case, be removed after she revealed that her husband works with a CNN legal analyst. Seminole County Circuit Judge Kenneth Lester Jr. is appointed to take her place.
April 20: Speaking during a court hearing, Zimmerman apologizes to Martin's family. Moments later, a Florida judge sets bond at $150,000, allowing Zimmerman the chance to get out of jail while he awaits trial.
April 23: Zimmerman enters a written not-guilty plea after being released on bail shortly after midnight. He has been fitted with a GPS monitoring device that allows authorities to track his location, the sheriff's department says. Lee resigns as Sanford police chief, but city commissioners vote against accepting his resignation.