Spencer and you have been a couple for a little over six months, although he never told his team anything about it because he couldn't find the right time to do so, plus he was embarrassed because he knew Morgan would tease him about finally getting a girlfriend.
Anyway, Spencer and his team were working in a small town helping to solve a series of homicides in the community. When they finally figured out who was responsible and went looking for him, a shootout broke out between the suspect and the police, resulting in Spencer being shot in the neck.
You found out about this from a call from Penelope Garcia, who informed you what happened to Reid and that he was undergoing important surgery, and before entering he asked them to call you. Now you travel to that small town to see Spencer.