The last scene shows Cristina Yang's office door sign where it reads "Dr. Cristina Yang - Director of Cardiothoracic Surgery". However, Cristina is in a hospital in Zurich, Switzerland, hence the sign should be in German, not English.
During the early stages of the mall incident, agents identifying themselves from Homeland Security show up at the hospital in an attempt to interview the suspect. The Federal Bureau of Investigation has the lead role in criminal investigations of terrorist incidents. Thus, FBI agents would be at the hospital to conduct any suspect interviews.