Devon Mitchell, 19, died in a hail of bullets when he emerged from the Wachovia bank on Green Level Church Road using a hostage as a shield.
Mitchell appeared to be holding a gun to the woman's head, but investigators later determined he was not armed.
The medical examiner's report said Mitchell suffered wounds to his head and abdomen - including one that penetrated his heart.
There was no alcohol in his system.
Police said a teller who reported a robbery in progress called them to the bank February 10. The female caller said the robber had instructed her to telephone for the police.
The woman told the 911 operator Mitchell had a gun hidden in a hat, but that she couldn't see the weapon.
Police surrounded the bank and a standoff began around 3 p.m. and ended just after 6 p.m. when Mitchell emerged from the front door with a hostage.
Pictures from Chopper 11 HD showed the female hostage sink to the ground and officers opening fire. The hostage was not hurt.
In a news conference right after the shooting, Cary Police Chief Pat Bazemore said she stood behind the actions of her officers.
"This is absolutely not how we wanted this to end," she said.
Bazemore said her officers had been in negotiations with Mitchell, trying to convince him to give himself up.
The 19-year-old was a student at Panther Creek High School. Records showed he dropped out in 2008, but reenrolled recently as a freshman.
People who knew him told ABC11 he had been struggling before the shooting. During the standoff, Mitchell's 15-year-old sister anxiously awaited news from inside a pharmacy across the street.
A witness who was in the store with the teen said she also told others that he hadn't been himself lately.
"She said my brother hasn't been acting right. She said something was different about her brother and she didn't know why," recalled Amanada Evans.
Bazemore said there were seven hostages in the bank at the beginning of the standoff. Two were released very early on and two more were released later in the afternoon.