Yes there should be some corroboration from the 'he' or 'she' bus driver.
The bus driver joined the kids, didn't drive them, the kids ran from the school to the house. Since this was in the morning after buses had dropped the kids off, it would make sense there were some bus drivers still in the parking lot when the shooting happened and who would end up at the guy's driveway just as the kids did, gathering together to talk about what just happened.