Cormac had just finished binding a couple of lower level Death Eaters. It'd been easy enough, and he'd come out with just a few scrapes and bruises. He knew things were no where near over, so as soon as he'd sent the prisoners to Auror Headquarters via Portkey, he headed back into the fray.
He was just in time to see Rodolphus Lestrange down Cass. When Cass didn't get up, Cormac hurriedly ran in Cass' direction. He knew things were bad when Lestrange merely sneered at the body on the ground and moved away. This was something Cormac was glad of--he didn't relish having to battle Rodolphus when he was trying to get Cass to safety. He couldn't do both, and Cass had to come first.
He dropped to his knees by his friend, and quickly catalogued the damage. It was bad--he wasn't even certain Cass was breathing properly. There was only one thing to be done. Cormac took out his own emergency Portkey, not wanting to jostle Cass around looking for his own, and said the incantation that would bring Cass to the Shack. He could only hope someone would be able to help Cass, and that he wouldn't need his own Portkey later.