FUKUOKA (Kyodo) -- A 15-year-old female junior high school student has died after she and a boy attending the same school were stabbed Saturday at a fast-food restaurant in Kitakyushu in Fukuoka Prefecture in southwest Japan, according to local police.

The assailant, believed to be a man around 40 years old and about 170 centimeters tall, is on the run after the incident, the police said Sunday.

The injured boy, who is in the same grade as the girl, said they were "stabbed by a complete stranger."

According to the police, the man was wearing a gray top, black pants and what appeared to be yellow footwear. It remains unclear whether he had any connection to the slain girl.

The police said security camera footage showed the man stabbed the two students as they were waiting in line at the cash register shortly after he entered the restaurant on Saturday night. He remained silent during the attack.

Police have set up an investigation headquarters.