Random assists given to enemy team

I was in a game last night and died to a Jayce while rengar was in our jungle. When I looked at the death recap, Rengar has gotten an assist based on "Thrill of the Hunt status effect" . In all chat, he said he got a random assist for some reason that he actually got gold for, and credited to his KDA. I'm not sure if this is just with Rengar or is an existing bug on multiple champions, but this seems like a really big bug.