There are plenty of older documentaries, mostly mainstream posted on Youtube about this case. Here are a couple to view, one by an influencer, the other a mainstream media with interviews, dubbed in English.
The BELGIAN DEMON - Marc Dutroux
The Marc Dutroux Pedophile Ring: Government Officials, Murder & Satanic Sacrifices (VERY DISTURBING)
Wait, was he a pedophile and a murderer, or a murderer who killed pedophiles?
Edit: Unfortunately, Wikipedia confirms the former.