The operator of an upstate New York limo rental company was charged with criminally negligent homicide on Wednesday, four days after one of his vehicles was involved in a historically deadly crash, PEOPLE confirms.

Nauman Hussain, the 28-year-old operator of Prestige Limo, in Gansevoort, was taken into custody following a traffic stop, state police announced at a Wednesday afternoon news conference.

Both police and the National Safety Transportation Board are probing the circumstances of Saturday’s crash in Schoharie, after a stretch limo carrying 17 passengers and a driver plowed downhill through a T-intersection of two state highways.

All 18 people in the vehicle were killed. Two pedestrians also died after the limo struck an empty vehicle in the parking lot of an adjacent business.

The crash was the deadliest transportation-related incident in the United States in nine years.

The limo’s driver has been identified as 53-year-old Scott Lisinicchia.

His background and the history of Prestige Limo have both come under intense scrutiny, as investigators worked to determine what led to the crash — driver or mechanical error, some roadway factor or a combination of issues.

Authorities said Wednesday that, ultimately, Hussain was to blame.

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“The sole responsibility for that motor vehicle being on the road rests with Nauman Hussain,” State Police Superintendent George Beach II told reporters.

Beach cited multiple problems of which Hussain was aware, such as the limo having been ordered off the road in September and that Lisinicchia “should not have been operating” the vehicle.

Gov. Andrew Cuomo said Monday that Lisinicchia was not properly licensed.

An attorney for Prestige did not immediately respond to PEOPLE’s requests for comment. Representatives with the company have not responded to previous messages.

However, speaking with reporters after Hussain’s arrest was announced, an attorney for the family said investigators were being hasty and that Hussain would plead not guilty, the New York Times reports.

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“Even the most simple investigation, done well, takes months,” lawyer Lee Kindlon said. “And now because of the actions taken today, that time frame is compressed.”

Hussain is set to be arraigned on Wednesday night, according to state police.

Superintendent Beach declined to discuss the case at length, citing the ongoing investigations, and he could not say if additional charges were possible or if Hussain’s father, who is reportedly the owner of Prestige Limo, could be arrested.

Hussain’s father is out of the country, Beach said.

Kindlon said Hussain was not significantly involved in the daily operations of Prestige, instead leaving the bulk of work to his father, who is in Pakistan dealing with health issues, according to the Times.

Kindlon previously told CBS News that, though Prestige’s small fleet of vehicles had reportedly been cited for violations numerous times in the last year, most of those infractions were not serious and all of them “had been addressed and corrected.”

A state transportation spokesman disputed this and the said the limo involved in the crash had recently been determined to be “unserviceable,” according to the Associated Press.

Kindlon has also blamed the intersection where the crash occurred — a T where two state highways meet — which includes a notorious hill pitching downward until it runs into the other road.

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“I think [Lisinicchia] came up over that hill unfamiliar with territory,” Kindlon said in an interview with the Albany Times Union. “I think the state has been warned about that intersection for years and the Department of Transportation is just looking to point a finger.”

The limo passengers killed on Saturday were close friends, relatives and couples. They had hired the vehicle to take them to a local brewery to celebrate the 30th birthday of fellow passenger Amy Steenburg.