
Dr. David King had finished running the Boston Marathon when the bombs went off, and he rushed to the hospital to help.
CNN's Sanjay Gupta explains ricin and how deadly the poison can be.
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CNN's Dr. Sanjay Gupta talks to Wolf Blitzer about pictures of Albert Einstein's brain that were just released.
Dr. Sanjay Gupta goes to Massachusetts to get answers from the facility that made the contaminated injections.
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