Justin Bruening, Sarah Drew, and Jason Goerge were all members of the Grey's Anatomy cast. Sarah and Jason were series regulars while Justin was a guest star in multiple episodes.
Michael O'Neill was also on Grey's Anatomy as Gary Clark, the shooter.
6 people have had a role on Grey's Anatomy. Sarah Drew (April Kepner), Justin Bruening (Matthew Taylor), Jason George (Benjamin Warren), Skye P. Marshall (Mary Hodges), Madeline Carroll (Ivy Soltanoff), & Michael O'Neill (Gary Clark).
Samara Lee is a military dependant in real life.