It appears that many villagers (in Kampot’s Chhouk district) thought he was a sorcerer, and after the attack his son burned the house down with the body inside, to try and ease concerns in the village. This last happened in Kampot in 2013, and also in Kampong Speu in 2014.
This is crazy that this still goes on, and is not only tolerated, but people actually believe this stuff and feel better now that the guy is gone. It's an interesting article to read; here's the full article from the Post:
‘This was revenge’: beheading of Kampot healer accused of ‘sorcery’ shows dark side of superstition
The article ends:
It is unclear whether villagers care much about finding the perpetrator. In the week since the healer’s death, many say the village feels better, the mood lifted. Others confess they now fear being haunted by his ghost. “When he was alive, we were scared,” said 49-year-old resident Tep Torn, chuckling. “Now that he’s dead, we’re still scared.”