I too have researched hit men, face to face with one of them after he retired. He was the one who told me that the message is generally for a specific small group, maybe only one family, sometimes just one individual.
The idea is not to leave a message that X was killed, but that X is gone. No longer involved in the matter for discussion. Leave the question of why is X gone, was s/he killed or just what did happen to him/her? Leave the question, “Did X get scared and run or was s/he kidnapped and killed.” That slows any police reports allowing the scene to corrupted causing doubt by the investigators as to what did happen and placing the victims family as suspects.
Do not know if you can, at the very 'end' of this logic; conclude with certainty; this was NOT a professional job - made to look simply, seamy. Albeit; a New Jersey landfill; does carry a history and resonance; if only to those involved; who work with 'others' up the food (including Gov.) food chain.