Story highlights A witness speaks to CNN for a second time, offering new details of the shooting

She says she is certain it was a younger voice yelling for help

Members of Zimmerman's legal team question the witness' recollection

As outrage over the shooting death of 17-year-old Trayvon Martin continues to grip the nation, key questions remain unanswered over what happened the night of February 26 as conflicting accounts are given by witnesses and attorneys for both sides.

What is known is that Martin, wearing a hoodie, ventured out from his father's fiancee's home in Sanford, Florida, to get a snack at a nearby convenience store. As he trekked back to the home with a bag of Skittles and an Arizona iced tea, he was shot and killed by George Zimmerman, a 28-year-old neighborhood watch volunteer. Martin was unarmed. Zimmerman has said he acted in self-defense.

CNN spoke to a witness to the shooting for a second time Friday, who offered new details about what she saw. Zimmerman's attorneys, for their part, were quick to knock down her statements.

Here's what they said:

Who yelled for help?

A recording of a 911 call made the night of the shooting captured someone pleading for help. Zimmerman has said he was yelling for help, according to his family members and his account to authorities. Martin's relatives have said they are certain the voice heard on the 911 call is Martin's.

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"From the very beginning and I still do feel that it was the young boy," the witness, who wants to remain anonymous, told CNN Friday.

The witness lives in the apartment complex where the shooting occurred and saw the incident through her window.

She described the cries for help as "devastating, desperate," and something "that will really always stay with me."

When pressed if she could determine who was yelling, the witness said "it was the younger, youthful voice (rather) than it was the deep voice I heard when they were arguing."

Zimmerman's attorneys jumped on the witness' characterization of Martin as "the young boy."

"I'm not sure when she came to that conclusion," said attorney Hal Uhrig, noting that when news of the shooting first broke, pictures of Martin as a 12-year-old were the first to circulate.

"The pictures you've put up tonight show a 6 foot 3 boy who was 17 years old," Uhrig said, pointing out that teenage boys can have voices that range from high to as low as a grown man. A police report listed Martin's height at six feet.

Audio experts Tom Owen and Ed Primeau, who analyzed the 911 recordings for the Orlando Sentinel, said they don't believe it is Zimmerman who is heard yelling in the background of one 911 call. They compared those screams with Zimmerman's voice, as recorded in a 911 call he made minutes earlier. In that call, in response to the 911 operator's question, Zimmerman described a "suspicious" black male, who ended up being Martin.

In describing her questioning by investigators, the witness remembered expressing that she should have done something more, in retrospect, after hearing the cries for help.

"The lead investigator said to me kindly, 'Well, if it makes you feel any better, the person that was yelling for help is alive,'" she recalled.

Who was on top of whom during the scuffle?

Zimmerman says he killed Martin in self-defense after the teen punched him and slammed his head on the sidewalk, according to an Orlando Sentinel report that was later confirmed by Sanford police. One of the responding officers saw a wound on the back of Zimmerman's head and a bloody nose, and noted that his back was wet, indicating he had been lying in the grass, according to the police report.

Martin's family and supporters say Zimmerman, who is Hispanic, racially profiled the teen, who was black, and ignored a police dispatcher's directive not to follow him. Zimmerman's attorneys interpret the call differently, and say the operator did not order Zimmerman not to follow.

"I know it was very dark, but I really would have to say that I thought it was the larger person on top," the witness said, referring to the heavier build of Zimmerman.

Craig Sonner, another Zimmerman attorney, questioned how the witness could determine the identities of those on the ground at that time of night and from her vantage point.

"I think it was dark, and I don't think she's sure what she saw," Sonner said.

The police investigation:

The Sanford police department has come under intense scrutiny for its actions following the shooting, and protesters have called for the firing of police Chief Bill Lee, who stepped aside temporarily last month amid criticism.

The witness declined to characterize her questioning by investigators as "in depth," instead saying "I just kind of told what I saw and heard."

She noted that when she offered to show the investigators where she saw the scuffle occur, she was told, "Nah, we don't need to see it."

She added that two phone calls to the lead detective have gone unanswered.

Her attorney, Derek Brett, said a follow-up visit on behalf of the state attorney's investigation on Wednesday yielded only 15 minutes of questioning.

"It was very general," Brett said, adding that had he been in the investigators' position, he would have had her recount her story again.

The state attorney's office declined to comment Friday, citing the ongoing investigation.

Sanford police did not respond to requests for comment Friday.

What will happen next?

A grand jury is expected to convene next week and could take up the case. Whether a grand jury will choose to indict, Sonner said: "we don't know."

Until now, only friends and relatives of Zimmerman's have come forward to offer his side of the story. Uhrig said Zimmerman "would love to be able to do that right now," but due to threats to his safety and the possibility of charges, he can't.

"There's going to be a time, hopefully in the fairly near future, where he'll have an opportunity to tell the public exactly what happened," Uhrig said.

Until then, Sonner cautions against jumping to conclusions.

"Everybody wants to know what happened, but we need to take a step back and let the evidence come out," he said.