PITTSBURGH — The parents of a 2-year-old boy who was fatally mauled after falling into a wild African dogs exhibit last fall filed a lawsuit Thursday against the Pittsburgh Zoo & PPG Aquarium, claiming officials had ample warning that parents routinely lifted children onto a rail overlooking the exhibit so they could see better.

WASHINGTON — President Barack Obama on Thursday defended America’s controversial drone attacks as legal, effective and a necessary linchpin in an evolving U.S. counterterrorism policy. But he acknowledged the targeted strikes are no “cure-all” and said he is haunted by the civilians unintentionally killed.