It probably seems like a drug over dosage. Large doses of Percocet or even Xanax can cause respiratory depression
and sudden cardiac arrest
I am sorry, but your nephew may not have informed you about it. Frothing in the mouth happens in poisoning
and drug over dosages because of the piled up secretions in the airway and aspiration.
The prior vomiting could have added to the dehydration
A Post Mortem report will be able to confirm the cause of death in him.
I am sorry about his death.