TOKYO (AP) – A 17-year-old boy armed with a sashimi knife stabbed a teacher to death and wounded two other adults Monday at his former elementary school, then stood in the faculty lounge and smoked a cigarette with the bloody blade still in his hand.

No students were injured in the midafternoon attack, the latest in a series of rampages in Japan involving knives and children.

Police said the teen, who refused to talk after his arrest, used the 8-inch knife usually reserved for cutting raw fish. Such blades are extremely sharp and are normally only accessible to trained chefs.

Terrified teachers watched the boy from the edges of the faculty room where he was found, as he held the knife in one hand and a cigarette in the other, said a police spokesman, Isoo Noda.

The attack panicked the 600 students and 30 teachers at the public school in Neyagawa City just outside Osaka in western Japan. TV video showed small children, guided by adults, running from school buildings.

“I couldn’t believe it,” principal Hirokazu Sakane said at a news conference. “It is unforgivable. It is especially mortifying that a staff member lost his life.”

Police did not release the boy’s name because he is a minor, but Hirokazu Kashiyama, an official with the local board of education, said he was a graduate of the school.

Mitsuaki Kamozaki, a 52-year-old teacher, was fatally stabbed in the back. A 57-year-old female instructor had deep knife wounds in her stomach and a 45-year-old school nutritionist was also treated for serious injuries.

Television station TBS reported that the boy, when younger, had written that his dream was to become a video game creator or game magazine editor when he grew up.