An attacker hacked seven children and one teacher to death Wednesday and wounded 20 others in a violent rampage at a kindergarten in northwest China's Shaanxi province.The slaying marked the latest in a string of attacks on schools nationwide and came despite an ordered boost in security at school grounds.Liu Xiaoming, deputy director of the propaganda department of Hanzhong city where the latest attack occurred, confirmed the deaths and injuries and said the attacker had killed himself afterward.