Bethenny Frankel's boyfriend started the binge that killed him Thursday night and realized he was in trouble.
We're told the NY medical examiner's office will determine the cause of death, although it is believed drugs were involved.
The medical examiner confirmed to Fox News that the man was Shields, its office is now investigating the cause of death and are awaiting an autopsy.
He was pronounced dead shortly afterwards.
The New York City Office of the Chief Medical Examiner (OCME) said Friday in a statement it was investigating the death of a man who was "believed to be" Dennis Shields and that an investigation was ongoing.
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In February, a source told PEOPLE the pair weren't together, but said Dennis was an important part of the RHONY star's life.
He had asked his 29-year-old assistant to administer Narcan - used to reverse an opioid OD - around 9 a.m., but it was too late.
Frankel and Shields were longtime friends before starting a relationship a couple of years ago. "His spirit lives on in our children". She explained that if they weren't "being teammates and it's not working, and one man is down, then the other man is down". "So both partners have to say, 'All right, I'm in it for this", said Frankel.
So far, Bethenny has yet to comment on the sad passing of her former boyfriend.
She added that they were trying to be good teammates and partners, and she thinks that relationships are "a little bit like a business".