Police have summoned a U.S. soldier stationed in South Korea to appear for questioning on Thursday in a stabbing incident.

The private first class, identified only as Christopher, is among five U.S. soldiers who were detained on Saturday after a street commotion in western Seoul. Christopher is suspected of stabbing a Korean man who was trying to stop the soldiers from making a disturbance.

The victim is reportedly in serious condition in hospital. The Eighth U.S. Army earlier expressed its regret over the incident and promised thorough investigations.