A 12-year-old junior high school boy was stabbed Tuesday morning by a 13-year-old male classmate as they were on their way to school in Suwa, Nagano Prefecture, police said.

The victim was rushed to a hospital, where it was determined that the lone stab wound had penetrated his lung. Doctors said he is conscious.

Police have taken the other boy into custody and are questioning him regarding the motive behind his actions.

According to police, the stabbing took place at around 7:55 a.m. as the two were walking to school with four other students. Police said they suspect an argument broke out between the two boys and are questioning the others who were at the scene.

School officials said the two boys had attended the same elementary school and both are members of the junior high soccer club. The two were friends, as far as the school could tell, they added.