A family of four from Massachusetts who were killed when a bus crashed into multiple vehicles in Virginia were traveling to a wedding with a carload of homemade desserts for the celebration.

The family wedding will go forward Sunday in South Carolina, but it also will be a time to mourn the loss of Dmitri and Ecaterina Doncev and their two children, Emily and Mark, a relative said Saturday.

"A son, a father — the whole family — everyone that has been dear to us," Carolina Bublik said.

The Doncevs were killed when a motorcoach caused a chain-reaction crash with vehicles that had slowed down for a work zone on Interstate 95 in Stafford County around 2:35 a.m. Friday, authorities said.

READ MORE: Bus crashes into cars on Virginia interstate, killing 5 people, state police say 

The bus struck an SUV driven by Priscilla Mafalda, 25, of Worcester, Massachusetts, whose vehicle then hit an Acura carrying the Doncev family, police said. Mafalda also died.

More people were treated for injuries, including one who was in critical condition, though most were discharged, Mary Washington Healthcare said.

The bus driver, Jing S. Dong, 48, of Staten Island, New York, was charged with two counts of involuntary manslaughter, and additional charges were likely, Virginia State Police said. It was not immediately known if he was in custody or had a lawyer yet.

The National Transportation Safety Board is investigating the crash, a monthslong task separate from the work of state police. NTSB board member Tom Chapman revealed few new details but said the bus was moving at a high rate of speed.

"It seems fairly clear that if there was any braking there wasn't much, because of the speed and severity of the collision," Chapman said.

The bus, which was taking people from New York to North Carolina, was operated by E&P Travel Inc., based in Kings Mountain, North Carolina.

Chapman said the driver's language proficiency would be part of the NTSB investigation. U.S. Transportation Secretary Sean Duffy, citing police, said on social media that Dong, a native of China, does not speak English.

Dmitri Doncev, 45, was a nurse who worked at Holyoke Medical Center. Ecaterina Doncev, 44, was a hairstylist who spent days making desserts for the family wedding, Bublik said.

They emigrated to the U.S. from Moldova in 2008 and settled in Greenfield, Massachusetts, she said.

Dmitri and brother Iuri tried to stay together while traveling in separate vehicles to South Carolina.

"At some point they ended up getting separated," Bublik said. "Dmitri said, 'You go ahead. I'll catch up later.' It was a big shock when Iuri arrived at the house. Dmitri should have arrived around the same time. When his car did not show up, and he wasn't picking up the phone — that's when the family started panicking."