Timeline of events in Trayvon Martin case Teenager Trayvon Martin is shot and killed on February 26 The investigation is continuing (CNN) -- Here's a look at the timeline of events in the shooting of Trayvon Martin in Sanford, Florida, and the ensuing uproar. February 26 About 7 p.m.: George Zimmerman, a 28-year-old neighborhood watch captain, calls 911 to report "a suspicious person" in the gated community called the Retreat at Twin Lakes. He is instructed not to get out of his SUV or approach the person. Zimmerman follows anyway, and moments later, neighbors report hearing gunfire. About 7:10 p.m.: Phone records show Trayvon Martin was on the phone with his girlfriend around the time he spotted George Zimmerman. At a March 20 news conference, Martin family attorney Benjamin Crump says the girl hears 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 in which the earpiece falls out of Martin's ear, and the connection goes dead, according to Crump. About 7:25 p.m.: Martin is shot and killed while returning from a convenience store to his father's fiancée's home. The weather is rainy. Martin is unarmed and carrying a small amount of cash, some candy and an iced tea. 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. What witnesses say in the Trayvon Martin case? March 8: Trayvon Martin's father, Tracy Martin, family members and attorneys hold a news conference calling attention to the case. March 13: Sanford Police Chief Bill Lee says Zimmerman has not been charged because there are no grounds to disprove his story of the events. Divided town struggles with stigma March 14: CNN's David Mattingly reports that police have concluded their investigation and turned the file over to the state attorney, who would have to decide on 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 follows Martin. In one of the recordings, a voice screams "Help, help!" in the background, 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: Lee announces that he will step down temporarily as head of the department, which has been criticized for its handling of the fatal 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, politicos, 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." Saturday: A handful of members from the New Black Panther Party offer a $10,000 reward for the "capture" of George Zimmerman. Monday: Exactly one month after Trayvon Martin's death, rallies across the country call for Zimmerman's arrest. In Sanford, the City Commission holds a town hall meeting on the incident and its aftermath. Wednesday: Zimmerman's father, Robert, appears on television and says Martin threatened to kill Zimmerman and then beat him so badly Zimmerman was forced to shoot. Thursday: 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 Trayvon Martin before he fatally shot the teen. CNN's Chris Lett and Diane Laposta and the CNN Library staff contributed to this report.