Per Voice of America (US Condemns Gaza Cease-fire Violation), the US acknowledges that this is what happened:
U.S. Secretary of State John Kerry, who with U.N. chief Ban Ki-moon had announced the 72-hour cease-fire late Thursday, in a statement Friday decried its “outrageous violation" and called for the missing soldier's immediate release.
Kerry called upon the international community to "redouble its efforts to end the tunnel and rocket attacks by Hamas terrorists on Israel and the suffering and loss of civilian life."
White House spokesman Josh Earnest, speaking on CNN, said the attack posed a "barbaric violation of the cease-fire agreement'' and repeated the call for the Israeli soldier's release.
The United States urged the international community to condemn the Hamas cease-fire violation in the "strongest possible terms,'' Earnest said.
The UN, on the other hand, isn't ready to admit wrongdoing by Hamas. From the International Business Times (Gaza conflict: Israeli soldier reportedly captures as ceasefire unravels):