What is infanticide? What incident made Fossey aware that it exists among gorillas?

Fossey notes that Curry was her "introduction to infanticide" among the gorillas. Infanticide is the killing of an infant. In this case, the infant was Curry. It is not fully explained what happened to Curry, but says that it seems an unknown silverback had attacked the group and that Curry had been bitten and killed, though she doesn't say whether it was the silverback or some member of Curry's group that killed him.