ZAGREB, Croatia—A 56-year-old man is suspected of killing three young children in Croatia’s capital Saturday, authorities said, while local media identified the man as the children’s father. The state prosecutor in Zagreb said the suspect, an Austrian citizen, was suspected of “grave murder… at the harm of three underage children.” Police said earlier that officers found the children’s bodies and a man in poor condition in a Zagreb apartment around 2 a.m. after they had been informed of an attempted suicide. The children had been killed, and the adult was taken to a local hospital, a police statement said. The news outlet Index said the children were 7-year-old twins, a boy and a girl, and a 4-year-old boy. The killing shocked Croatia, triggering questions about potential previous violence within the family. Social care service official Margareta Maderic said this was not the case. “Family should be a place where children …