TIL if someone else kills a dragon, you still get its soul

hello all Dovakhiin, first post here. so, TIL that you cant absorb dragons soul even if you do not killed him. happened to me today, while fighting a random frost dragon. the dragon flew away from the battle, because he saw a group of forsworn started to shoot arrows at him. he eventually got mad but not mad enough because they slayed him. i was watching this from the hills and the dead dragon just lied there for 3 minutes, when i decided to go check the loot. and to my surprise he started burning n shit, and i got its soul.

sorry, for my poor english, not my language.