The modified limo that crashed and killed 20 people wasn't even supposed to be on the road, New York's governor said Monday. On top of that, the driver "did not have the appropriate driver's license to be operating that vehicle," Gov. Andrew Cuomo said. The startling revelations brought more anguish to those grieving the deaths of 20 people in the quaint town of Schoharie. At least one victim seemed worried about the condition of the limo, according to text messages shared with the New York Times. Before the disaster, the limo was full of exuberance -- 17 birthday party guests who had many reasons to celebrate. There were newlyweds and young couples and four sisters, on their way to revel at an upstate New York brewery. But for reasons still unknown, the limo plowed through a stop sign and crashed into a parked SUV, causing the deadliest US transportation accident in almost a decade. All 17 passengers were killed. So was the limo's driver and two pedestrians. As more details emerge about the apparent broken rules, investigators also are wondering whether the unusual structure of the limo may have contributed to this mass tragedy. Federal, state and local investigators flooded Schoharie to try to understand what happened. "We don't know the cause of the accident, if it was a vehicle malfunction, if it was a driver malfunction (or) a driver error," Cuomo said.