South Korean police said Monday they had launched an investigation into a high school student on suspicion of inflicting bodily injury on a security guard in his 60s, after a video of the attack sparked public outrage.

Nambu Police Station in Namyangju, Gyeonggi Province, is questioning the suspected attacker. The security guard had scolded the teen and his friends for causing a disturbance Friday at a commercial complex in Dasan-dong, Namyangju, which is believed to have led to the assault.

The video was posted on social media by the suspect's friend, who claimed that it was a "sparring match" that was suggested by the victim himself. The friend also said it was the victim that told them to film the incident.

Police had initially decided not to investigate the case when the victim said that he did not want the boy to be punished: Assault is among the crimes that cannot be punished upon the victim's refusal.

But the incident and the viral video of the attack sparked a nationwide furor, after which officials decided to investigate the teen on suspicion of bodily injury on another -- which is a crime that can be criminally punished regardless of the victim's wishes.

The suspect told the police that he was deeply sorry for his actions. Officials are also investigating the claim that the fight and the filming took place with the consent of both parties.