Arrest made after 800-pound boulder rolls off truck and kills driver and her daughter

An 800-pound boulder rolled off the back of a truck and killed a 67-year-old driver and her daughter in Minnesota, authorities say.

Karen and Jena Christiansen suffered blunt force trauma to the head when the boulder dislodged from the truck and hit their Toyota Avalon in Rosemount.

Truck driver Joe Czeck was arrested on Wednesday, two days after the tragic accident. Investigators used surveillance video to identify the truck as belonging to his company, Czeck Services.

Karen Christiansen and her 32-year-old daughter, who was in the front passenger seat, both died at the scene, according to the Pioneer Press.

"It’s very rare, but it does happen," Rosemount Police Chief Mitchell Scott told the newspaper. "That’s why it’s so important to slow down and make sure loads are secure, because you’re taking other people’s lives in your hands."

Scott told the Star Tribune that the boulder was about 3 feet by 3 feet.

"We had a connection like no other ... my heart is broken .. the world has lost an angel," Jena Christiansen's boyfriend Ryan Kilian told KSTP.

Kilian said that Jena was the "most amazing" person he ever met.

"She was so smart and beautiful," he told KSTP. "She made me the man I am today I would be nothing without her. She would do anything for anyone who needed help she loved her family so much. She had an amazing sense of humor I literally have spent hours just talking to her."

Charges have not been filed against Czeck, who was booked into the Dakota County Jail.

"I think you would have to know that it fell off the truck," Chief Scott told KSTP. "That's something we'll have to figure out in the course of our investigation, once we are able to talk to the driver to see what was going through their mind."

• With News Wire Services