You weren't there, man. I had to leave them. There wasn't enough time for a rescue. I couldn't risk it. I'm sorry, but tough choices need to be made, sacrifices need to be sacrificed.
You weren't there, man. Just because they weren't all rotting and moaning doesn't mean they weren't walking dead waiting to happen. If I hadn't dropped a megaton or two of explosive force on their heads, they'd have been food for the zeds anyway. I did them a favour.
You weren't there, man. Sure, there were a few hundred bleating mouthbreathers expecting a pickup as a few thousand undead charged into the square. But there was a scientist who needed rescuing. Scientists are how we're going to win this war, with their research into bigger explosives and such.