If Aubrey's injuries were on his back, he would be immobilized laying on his stomach or side, not sitting up in a hospital bed.
Angela tells Cam that D.C. has a system called Shots Fired that helps to triangulate where a gunshot originated in the city. Since this was a crucial tool in identifying Brodsky as the person who killed the Gravedigger years earlier and they've all been working in D.C. for 10 years, there was no reason for Angela to treat this as new information.