Cassidy, a former head of the firefighters union and current vice chair of the FDNY pension fund, was arrested just before midnight Tuesday after his vehicle jumped the curb on Seventh Ave. near W. 30th St., authorities said.
Witnesses said he tried to bolt from the accident scene but was stopped and held by a pair of pedestrians.
Cassidy remained in custody Wednesday awaiting arraignment in Manhattan Criminal Court on the booze and drug charges. Police recovered a cocaine-filled yellow envelope tucked inside his wallet, officials said.
Eyewitness Jakob Grabel watched an incoherent Cassidy lurch from his car and collapse to the ground after the accident.
He looked “bewildered and out of it,” recalled Grabel. “He got out of the car and tried to walk off but two good Samaritans stopped him. I called 911.
“He was mumbling gibberish, not speaking any proper English,” the student added.
Cassidy, 62, identified himself as a fire marshal to two witnesses, according to Grabel.
A source indicated Cassidy could face additional criminal charges for impersonating a fire marshal. There was no response for comment from the FDNY, and the fire union declined comment.
The officers were “calm and courteous” and at one point placed their hands on Cassidy’s back to keep him from stumbling, a video shot by Grabel showed.
“I think people from different backgrounds would have gotten cuffed easily,” said Grabel, a student at the Fashion Institute of Technology.
Cassidy, the father of two, is currently separated from his wife. According to a source, Cassidy was recovering from double knee surgery and taking prescription medicine before having a few drinks.
The mix of meds and alcohol may have contributed to his woozy state, the source said.
Nobody was injured in the accident, and police said Cassidy had no prior arrests. It was unclear where Cassidy was coming from or where he was headed when his vehicle went up on the sidewalk.
Cassidy also appeared to violate city conflict of interest laws that bar employees from using government cars for personal business.
In 2016, City and State named Cassidy one of the city’s 100 most powerful people.
Cassidy was the first Uniformed Firefighters Association head to be elected directly from a firehouse, according to his bio.
The UFA is the largest fire union in the U.S., with about 8,500 active and 15,000 retired members.
In 2016, he left the union post to become the lead trustee and vice-chairman of the FDNY Pension and Investments Board — a move that raised the hackles of union members who saw his new job as a betrayal of the rank-and-file.
Critics accused Cassidy of violating the so-called “turncoat provision” passed after previous union president Tom Von Essen became fire commissioner under then-Mayor Rudy Giuliani.
The provision barred union officials from going to work for the city for three years after stepping down from their union duties.
As union president, Cassidy pushed for compensation for firefighters and first responders who suffered from the environmental effects of the 9/11 attacks.
He advocated for separate acknowledgment of emergency responders on the 9/11 memorial — in opposition to Mayor Michael Bloomberg, who favored a random list of names.