MSF
The unannounced incursion of a U.S. armored vehicle could strengthen the case for an outside probe of the attack.
The raid hints at a motive for the strike.
"We are working on the presumption of a war crime."
WHAT'S HAPPENING
NATO forces struck two oil tankers, killing about 100 people, in the same town where the Doctors Without Borders hospital was hit.
He suggested the tragedy could have been avoided with more U.S. involvement.
Hundreds are feared dead after their boat capsized off the Libyan coast.
