NEW BRUNSWICK - Injuries sustained in yesterday's bombings at the Boston Marathon were similar to the types of casualties normally seen on the battlefield, and are difficult to prepare for.

Trauma doctors and surgeons in Boston faced with incredible carnage had to put aside emotions and concentrate on saving lives.

Massachusetts General Hospital Doctor George Velmahos says, "These patients came to us with completely mangled, destroyed extremities, hanging by shreds of muscle and skin."

Many hospitals hold disaster training drills to prepare for that kind of mass casualty event. Robert Wood Johnson University Hospital in New Brunswick has a big emergency drill planned for Saturday.

"You can't duplicate the terror that certainly was part of what happened in Boston," says Dr. Vicente Gracias at RWJ. "But at the same token, we do try to prepare as much as we possibly can."