Less than 30 hours after a video was released online showing three juveniles assaulting a boy with a concrete brick, Beijing police said on Monday that they have detained the alleged suspects.

According to the micro blog of the Beijing Public Security Bureau, the three suspects are juveniles, with the oldest born in 1997.

One of the suspects, who is surnamed Guo and is from Henan province, surrendered himself to police on Monday morning accompanied by his family. The other two suspects, who are both from Gansu province, were arrested in Hebei province, the public security bureau said.