Pennsylvania car crash kills six September 3, 2013 -- Updated 0338 GMT (1138 HKT) The cause of the crash is not clear; among the dead are two children "It's just heart wrenching," says superintendent (CNN) -- Staff will be on hand Tuesday to help students grieve after a weekend car crash in northwestern Pennsylvania killed six people, including two children. For unknown reasons, one car crossed the center line, striking another head on, according to state police. Two people in the first car died; four in the other. Among the deceased were a 12-year-old girl and a 6-year-old boy. Both children were students in the Kane Area School District, CNN affiliate WTAJ said. The message to kids is -- it's OK to feel sad. This was real, and it was tragic," said elementary school counselor Steve Wolfe. Superintendent Maryann Anderson and her staff have set up a plan to help students process what happened and will offer sessions at night so that parents can attend, according to WTAJ. "If you lose a child, no matter where you are, it's just heart wrenching," she said. The crash took place Saturday afternoon in McKean County. It's under investigation.