We have our answer: It was Synthetic Cannabinoids, per New York Times article

Weeks after he collapsed in the preschool parking lot, doctors from the New Jersey Poison Control Center tested the contents of his Neptune’s Fix bottles. Results included synthetic cannabinoids and other unlisted ingredients as well as tianeptine..

Welp, It was Synthetic Cannabinoids

I don't know if this was ever actually proven.

But this does for me

Well, this whole thing was written like someone was doing a favor for the DEA, including scare mongering about Kratom

This could have a swift impact on the availability of Tianeptine

We gotta get ready for the end of Tianeptine to come.

Will be a surprise for ER's around the country for sure.

https://www.nytimes.com/2024/01/10/health/gas-station-heroin-tianeptine-addiction.html?smid=nytcore-ios-share&referringSource=articleShare