3 killed when school buses crash

• NEW: Three victims were female, police spokesman says


• NEW: One bus appears to have swerved across median and hit the other


• NEW: My grandson was "petrified," family member says


• NEW: Schools won't hold classes Wednesday, but counselors will be there

(CNN) -- Three people, including two young girls, were killed when two school buses crashed in Knoxville, Tennessee, officials said Tuesday.

Knoxville Police Chief David Rausch told reporters the children on the bus were in kindergarten through third grade. An female aide on one bus was killed in the accident, which occurred at about 3 p.m.

Woman: Grandson 'petrified' by bus crash

"(My grandson) was in shock. He was crying. He was petrified," Gloria Johnson told CNN Knoxville affiliate WVLT. "A bus is supposed to be safer than a car."

At least 23 injured children were taken to hospitals. Some were transported by emergency vehicles; some were driven by their parents, the chief said. One hospital said 20 children were treated there and released.

The two buses were traveling in opposite directions on Asheville Highway near Governor John Sevier Highway when one made a sharp left turn, crossed a concrete median and struck the side of the other bus, a spokesman for the police department said.

Spokesman Darrell DeBusk cautioned the media that the investigation is still in its early stages.

After the collision, the bus that was struck flipped on its side and slid down the road, DeBusk said. The three people who died at the scene were on the overturned bus.

The other vehicle sustained front-end damage. The driver of that bus was taken to the hospital and treated for non-life threatening injuries. It was unclear whether the other driver also was hospitalized.

Authorities were still trying to notify the families of the deceased, DeBusk said.

The buses served different elementary schools, which are about 3 miles apart.

"Our families and community suffered an unspeakable tragedy today, and our thoughts and prayers are with all of the families and staff members at Chilhowee Intermediate School and Sunnyview Primary School," Knox County Schools Superintendent Jim McIntyre said in a written statement.

The two schools won't hold classes Wednesday, but counselors will be there to lend support.

CNN's Kevin Conlon contributed to this story.