01/31 NEW YORK (UPI) -- The bullet that killed a hostage in a West side shootout was fired by a city police officer, prompting a department investigation and drawing anger from her family Sunday. Aurea Bonnie Vargas was used as a human shield by a fleeing bank robber and was cut down by a .38-caliber bullet similar to police ammunition, the medical examiner's office determined Saturday. The bullet pierced the heart, lung, spine, esophagus and aorta of the East Harlem teacher's aide, the autopsy revealed. Vargas and the robber who grabbed her as she left her West 93rd Street apartment building Friday died in a hail of bullets, with police firing 46 shots. The robber, Sidney Fisher, 24, of 1707 Branch Drive, Mays Landing, N. J., fired at police, whose bullets struck him 12 times. Fisher was part of a group of four gunmen who held up a nearby Chemical Bank branch. Two suspects are in custody, charged with murder and robbery, and a fourth is being sought. The medical examiner said Vargas was struck by a total of three shots. Two were ricocheting 9mm copper-plated bullets, but Officer Peter Friscia, a police spokesman, said it was undetermined who fired those shots. The gunman was armed with a 9mm handgun, as are some city police officers and all transit police, two of whom were on the scene. Two police officers suffered minor injuries. "They forced the guy to shoot his way out," said Vargas' distraught brother Raymond Vargas Santiago, who lived with the victim and their father in a groundfloor apartment. Vargas Santiago said no city officials had contacted the family. He slammed police for their response to the holdup and to his sister's death. Police Commissioner Raymond Kelly announced Saturday night that he ordered formation of a Hostage Situation Review Comittee to study procedures used by police in such events. "The tragic outcome of Friday's events highlights the volatile nature of these encounters. When people think of hostage negotiations, they usually have in mind a stationary situation in which a hostage is being held, often inside and a skilled negotiator has the opportunity to bargain with the hostage taker," he said. "Yesterday the incident was mobile, two police officers were shot and events unfolded with life-threatening speed," he said, announcing three top officials would examine police procedures.