Resolve Runes (Guardian)

So not to be a negative nancy or anything, but I just finished a match against a Rakan running the Guardian rune. I'm still learning the ins and outs of "Runes Reforged" but something peculiar happened. My team and I killed Rakan bot while he was by himself. As he lie there, Varus approached his body. When I dashed in to do damage to Varus, Rakan's Gaurdian Rune proc'd, shielding Varus for a period of time., whilst Rakan was still dead. Is this intentional? Or did i find a possible bug? I'm asking mostly out of curiosity so I know how to better plan my advances.