how to pull entities to a another entities

I have set a mob (tortos) and I want the mob to attract other mobs around it when it dies. (actually I want it to pull all mobs but I didn't know how to choose it) this procedure
From a video of NorthWestTrees, I couldn't adapt it to my mod. how will I do.
Even in the procedure, I couldn't understand exactly what was going on. What does the last if do part do? What is yaw and pitch?

img:https://imgur.com/a/Wuti6w3