SAN ANTONIO -

The driver of a pickup trucks slams into the back of Southwest Independent School District school bus.

The accident happened just before 7 a.m. at Shepherd Road and Interstate 35.

Crews say the driver failed to stop and rammed into the back of the bus.

There were 23 middle school students on the bus.

The bus driver, along with three students and the driver of the truck, were all sent to an area hospital. The three students only suffered minor injuries.

Anne Marie Espinoza, director of communications for Southwest ISD, said the children were experiencing minor aches and were sent to the hospital for "precautionary measures."

It's not clear why the driver failed to stop.

Investigators believe he may have suffered a seizure behind the wheel in time and if he will face any charges.