Buffalo gunman’s video is surfacing on Facebook, sometimes with ads beside it.

People searching on Facebook for footage of Saturday’s racist shooting rampage in Buffalo, N.Y., may have come across posts with footage of the attack or links to websites promising the gunman’s full video. Interspersed between those posts, they may have also seen a variety of ads.

The social network has sometimes served ads next to posts offering clips of the video, which a gunman live streamed on the video platform Twitch as he killed 10 people. For the past six days, recordings of that livestream have circulated across the internet including on Facebook, Twitter and fringe and extremist message boards and sites, despite some companies’ efforts to remove the content.

The pace at which an 18-year-old gunman’s ephemeral livestream morphed into a rapidly proliferating, permanent recording shows the challenges large tech platforms face in policing their sites for violent content.

Facebook and its parent company, Meta, rely on a combination of artificial intelligence, user reports and human moderators to track and remove shooting videos like the Buffalo one. But in some search results, Facebook is surfacing the violent video or links to websites hosting the clip next to ads.