Yes it was definitely Don Tomassino who was injured in the murder of Ciccio. Vito went back and pulled himinto the car, and we see him again at the railroad station in a wheelchair.

Don Tomassino is a central character to all three movies. He is someone who Don Vito thought of as an equal, a partner. Michael was sent to Sicily under Don Tomassino's protection, and other than Vito, and possibly his first wife, I don't think Michael really loved anyone as much as Don Tomassino. Certainly Michael learned a great deal from him, and was even relying on him to save his bacon in GF III when Don Tomassino arranged for the meeting with Cardinal Lamberto. It is also at his casket where Michael breaks down and realizes that his life has been a waste.