A suspected drunk driver, who police say crashed his truck into a crowd of people during a Fourth of July celebration in New York City on Thursday – killing three and injuring eight, is a wellness advocate and a substance abuse counselor, sources say.

Daniel Hyden, 44, of New Jersey, was driving a Ford F-150 pickup truck at a high rate of speed when he ran a stop sign at an intersection, mounted a sidewalk and smashed into a group who were enjoying the evening at Corlears Hook Park in the Lower East Side at around 9 p.m., police said. 

Three people have now been confirmed dead – Lucille Pinkney, 59, and her son, Hernan Pinkney, 38, as well as an unidentified female – after the holiday celebrations turned deadly in horrific circumstances.

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Eight other victims were injured, including an 11-year-old child.

"Responding officers who did arrive on the scene did smell some alcohol," said NYPD Chief of Department Jeffrey Maddrey said at a late-night police briefing. "There were people who were there at the scene who grabbed the driver, removed the driver and made sure the driver didn't leave."

So far, Hyden has been charged with three counts of driving while intoxicated with alcohol or drugs, and one count of operating a vehicle without a license. He is expected to be hit with several more charges.

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Hyden reportedly wrote a book titled "The Sober Addict," which claims to be a guide on "how to be functional with the dysfunctional disease of addiction."

"This guide will help you learn how to function with this dysfunctional and chronic illness," the book’s bio on Amazon reads. 

Hyden’s Amazon author bio lists him as a substance abuse counselor, instructor and public speaker. The New York Post was first to report that the suspect in the case had penned the book.

Responding firefighters found the four victims – including the three deceased – underneath the truck when they arrived on the scene.

"They used their airbags, floor jacks and cribbing in order to lift the vehicle off of the victims," FDNY Assistant Chief Michael Meyers said at the press conference.

Video from the scene shows the front of the truck smashed, and it is surrounded by several park benches and debris like empty cups strewn across the floor. 

New York City Mayor Eric Adams also briefed the media and said that the victims were simply out celebrating when the deadly incident unfolded. 

"We had a tragic incident which took place here," Adams said. "A driver drove into a crowd of people who were actually just celebrating like so many New Yorkers and Americans are doing right now."

He said the incident was not terror-related.

Fox News' Alexis McAdams and CB Cotton contributed to this report.