(CBS NEWS) Rania Abu Anza's twins, a boy and a girl, were conceived after she spent more than a decade and three rounds of fertility treatments trying to become a mother. At just six months old, they were both killed Saturday, along with at least 14 other members of the Abu Anza family, in an Israeli strike on the southern Gaza city of Rafah. "What did these babies do," the bereaved mother asked, holding her babies' bodies. "What are you doing? Just watching us die?" After nearly five months of a war that has killed some 30,000 people in Gaza, according to its Hamas-run Health Ministry, the Biden administration issued its fiercest criticism of the conflict to date Sunday, with Vice President Kamala Harris labeling the situation in the Gaza Strip a "humanitarian catastrophe" and calling for an "immediate cease-fire." "People in Gaza are starving. The conditions are inhumane and our common humanity compels us to act," Harris said at an event commemorating "Bloody Sunday" in Selma, Alabama, where state troopers beat civil rights marchers on the Edmund Pettus Bridge nearly 60 years ago. Harris called for the Israeli government to do more to increase the flow of aid to Gaza to ease the suffering there, adding that there could be "no excuses."