Outrage, protests grow over shooting of unarmed Florida teen NEW: Shooter paced near the body, "kind of 'Oh, my God, what did I do," neighbor says NEW: Another neighbor said shooter was "straddling" the teen after the shooting The 17-year-old was not armed when he was killed last month His killing also sparks a petition demanding his shooter's arrest Sanford, Florida (CNN) -- Outrage over the killing of an unarmed Florida teen rippled nationwide as supporters planned more protests Wednesday and a petition demanding the shooter's arrest amassed nearly 1 million signatures. Trayvon Martin was fatally shot on February 26 while walking to the house of his father's fiancee in Sanford after a trip to a convenience store. George Zimmerman, a neighborhood watch leader, said he killed the teen in self defense. Nearly 750,000 people have signed a petition on Change.org demanding Zimmerman's arrest, making it one of the website's largest campaigns. On Wednesday, supporters will gather in New York City for a "Million Hoodie March," a reference to the attire the 17-year-old was wearing when he was shot. A black person in a hoodie isn't automatically suspicious. Let's put an end to racial profiling," the protest page said. Zimmerman has not been arrested or charged in the killing of the black teenager. A police report describes him as a white male, but his family says he is Hispanic. The February 26 shooting occurred when Zimmerman -- who was patrolling the neighborhood -- saw the teen walking home after buying candy and a drink at a convenience store. Zimmerman called 911 and reported what he described as a suspicious person. A few moments later, several neighbors called the emergency number to report a commotion outside. There has been a heated debate and questions over whether Zimmerman used a racial slur during the 911 call released this week. We didn't hear it, however, I am not sure what was said. So I never said we missed a racist remark," said Sgt. David Morgenstern of the Sanford Police Department. While some neighbors were still on the phone with the emergency dispatchers, cries for help followed by a gunshot sounded in the background. "The time that we heard the whining and then the gunshot, we did not hear any wrestling, no punching, no fighting, nothing to make it sound like there was a fight," said Mary Cutcher, one of the callers. Cutcher told CNN's "AC360" on Tuesday night that Zimmerman was confused after the shooting. "He'd pace and go back to the body and just like -- I don't know if he was kind of 'Oh, my God, what did I do? what happened?'" she said. Another caller, Selma Mora Lamilla, said she did not hear any altercation, but the teen cried and "whimpered" before the shooting. She described Zimmerman as "straddling" the teen after the shooting, saying he was "on his knees on top of a body." As the controversy rages, a lawyer for the victim's family said his girlfriend was on the phone with him during the incident and can help prove he was killed "in cold blood." The girl connects the dots and "completely blows Zimmerman's absurd self-defense claim out of the water," lawyer Benjamin Crump told reporters. Shortly before he was shot, the teen told her someone was following him, and he was trying to get away, according to the lawyer. The girl, who did not want to be identified, said that during the call, she heard the teen ask why the person was following him. She got the impression there was an altercation in which his earpiece fell out after he was pushed and the connection went dead, Crump said. She did not hear any gunfire, he said. Phone records show the teen was on the phone with her much of the day, including around the time of the killing, the lawyer said. Federal prosecutors and the FBI will investigate the incident, and a Seminole County grand jury will convene April 10, State Attorney Norm Wolfinger said in a statement. Police say they have not charged Zimmerman, 28, because they have no evidence to contradict his story that he shot in self defense. In a police report, Officer Timothy Smith said Zimmerman stated he was " yelling for someone to help me," but the victim's family said it was the teen asking for help. Trayvon's family said they believe race was a factor in his death, fueling an outcry in the racially mixed community 16 miles northeast of Orlando. Zimmerman's family has denied race played a role, saying he has many minority relatives and friends. CNN has made numerous attempts to contact Zimmerman, but has been unsuccessful. The shooting has renewed a debate over a controversial state law. Florida's deadly force law, also called "stand your ground," allows people to meet "force with force" if they believe they or someone else is in danger of being seriously harmed by an assailant, but exactly what happened in the moments leading up to Trayvon's death remains unclear. Zimmerman's father said his son never followed or confronted the teen, but 911 recordings tell a different story. During the incident, the teen started to run, Zimmerman reported. The case is rooted in one main thing, said Jeffrey Toobin, a senior legal analyst for CNN. On this issue, the evidence currently seems murky," Toobin said. Finding other witnesses is crucial because the teen is no longer here to give his side, he said.