According to the Jerusalem Post:
An anti-tank missile [or mortar] fired from the Gaza Strip landed near a bus in the Sdot Negev Regional council on Thursday, injuring two people. The bus driver was critically injured, and one passenger was moderately injured. They were the only people on the bus.
Ynet is reporting that one of those injured was a 16-year-old boy, whose situation was described as critical. I’ll try to update the story as more information becomes available.