Trayvon Martin's parents visited lawmakers in Washington. NBC's Jay Gray reports.
Wilson said Tuesday that she had a sign placed outside her office counting "the number of days that Trayvon Martin's killer is at large." She also briefly took it to the House floor.
The briefing, which isn't as formal as a congressional hearing, marks the first time Congress has waded into the controversy.
Ben Crump, an attorney for Martin's parents, told the panel that the family was convinced Martin was targeted for special attention because of his race, arguing that tougher laws against profiling might have averted the shooting.
Martin's father, Tracy Martin, urged lawmakers to make "sure that he did not indeed die in vain.”
The briefing came as details of the police report made at the scene of the Feb. 26 shooting were emerging.
ABC News, citing "multiple sources" whose affiliations it didn't identify, reported Tuesday that the lead homicide investigator in the case recommended that Zimmerman be charged with manslaughter but was overruled because the state attorney's office decided there wasn't enough evidence.
The investigator, Chris Serino, filed an affidavit on the night of the shooting stating he was unconvinced by Zimmerman's account, according to ABC, which said the state's attorney's office had no comment.
At least one witness, a 13-year-old boy, told police he saw a man fitting Zimmerman's description on the ground moaning before a shot was fired. In the original police report on the incident, a Sanford officer wrote that Zimmerman's "back appeared to be wet and was covered with grass, as if he had been laying on his back on the ground," and that he was bleeding from his nose and the back of his head.
Read the Feb. 26 incident report (below)
Zimmerman has said he shot in self-defense, and his attorney says he suffered a broken nose and other injuries when attacked by Martin.
A neighbor told Dateline NBC that she heard what she thought was the moaning of a young person followed by a gunshot. She said that she and her roommate saw Zimmerman straddling Martin's body and that he didn't appear to be trying to help him.
Special prosecutor Angela Corey called for patience Monday as her team of investigators continues looking into Martin's killing. She didn't say when officials would decide whether there was enough evidence to prosecute.
NBC News' Luke Russert contributed to this report.