depends on the country and the state but yea, that’s quite the risk to take. i still think op would be in less danger by being fined or even imprisoned for it than living with a traumatised teen who has resorted to cannibalism to deal with his grief. he needs to be seen to quite quickly and i doubt a mother all by herself has the power to do so :/

i think you should immediately report it, as the implication that he ate human meat only for months means that as soon as he ran out of your family members (may they rest in peace), he would have looked for it elsewhere. you may be in danger, and if not you, anyone he may encounter at a vulnerable time in their life