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A pickup truck smashed into a school bus stop in Washington on Thursday morning, injuring six children — two critically.

The middle school boys were waiting at a school bus stop in Maple Valley, Washington, when a man in a pickup truck apparently lost control of his vehicle, Kent Regional Fire Authority Spokesman Capt. Kyle Ohashi told NBC News.

Six students were injured after a pickup truck ran into a bus stop in Maple Valley, Washington on April 14. King County Sheriff's Office

The truck struck a mailbox before crashing into the bus stop, hitting four boys, Ohashi said. Two children were critically injured in the crash and driven to a local hospital, along with another child who suffered non-life-threatening injuries.

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Another boy was “clipped by the car,” but he wasn’t injured, Ohashi said. Two more children were injured by debris from the mailbox.

The King County Sheriff's Office said in a statement later Thursday that one of the boys suffered serious injuries to his chest and another suffered a broken leg. The other injuries ranged from a possible broken ankle to cuts and bruises.

The truck's driver struck a tree after hitting the boys and was found unconscious at the wheel with his foot still on the gas, the sheriff's office said in a statement.

The 19-year-old driver was arrested and being booked for multiple counts of investigation of vehicular assault, the statement said. He is believed to have suffered a medical issue prior to the crash the statement said, but was driving with a suspended license.

The driver is prone to seizures, according to NBC affiliate KING5.

The boys, students in sixth and seventh grade, were on their way to Cedar River Middle School in Maple Valley, said Kevin Patterson, director of communication for the Tahoma School District.

“We’re waiting for reports and we’re hoping the kids are OK,” Patterson said. “This is a terrible tragedy. Who could imagine something like this would happen?"

The school district has sent messages to all of the families in the district, he added, and the Cedar River Middle School principal was reaching out to the families of all the students who were injured. The district will have extra counselors on staff to help the students.