ROCHESTER, Ind. (AP) — A 9-year-old girl and her twin 6-year-old brothers were struck and killed by a pickup truck as they crossed a northern Indiana road to board a school bus before sunrise Tuesday, police said. A fourth child was critically injured and airlifted to a hospital.

A Tippecanoe Valley School Corp. bus had stopped and lowered its stop-arm on the road near Rochester around 7 a.m., just before a northbound pickup truck slammed into the children as they crossed the southbound lane, Indiana State Police Sgt. Tony Slocum said.

Six-year-old twin brothers Xzavier and Mason Ingle and their 9-year-old sister, Alivia Stahl, died at the scene, he said. The rural Rochester residents were students at nearby Mentone Elementary School.

The siblings’ great aunt, Pamela Pugh, told the South Bend Tribune that she was stunned and shaken by their deaths.

“I’m just trying to make sense of all of it. There are no words,” she said.

Slocum said an 11-year-old boy not related to the deceased siblings suffered multiple broken bones when he was also hit by the pickup. That child, Maverik Lowe, was in critical condition at a Fort Wayne hospital and was undergoing surgery.

Lowe was conscious and speaking to emergency workers before he was airlifted to the hospital, Slocum said.

Authorities were interviewing the pickup driver.

He said it was early in the crash investigation and it was unclear if the driver would face charges in the deaths, although he noted Indiana law requires motorists to stop when a school bus is picking up or dropping off children.

Slocum said the students had the right of way as they crossed the street from the rural mobile home community where they lived.

“It’s an unspeakable tragedy,” he said. “We all have a responsibility to share the roadway and we’re all responsible for making sure our children get to and from school safely.”

The Tippecanoe Valley School Corp. said in a statement posted on Facebook that counselors had been dispatched to its schools to help students, staff and parents and urged “the community to come together to pray for the families.”

Detectives were interviewing witnesses and a crash reconstruction team was at the scene near Rochester, about 100 miles (160 kilometers) north of Indianapolis.