How to go about animation for two characters

Hey, how would I go about creating an animation between two characters in a game exactly like this video
from 17-18 seconds?


Just as shown in the video, how would I accomplish this special kill animations where the player does a certain animation and the character being interacted with has a synced reactionary animation?
(Note: my player character is using the FPS template)

I would be grateful If anyone could give me a hand in the right direction or even link me a youtube video that could help me with this.

Would I just create separate animations for both characters and active them accordingly?