SANTIAGO, Chile (AP) — Authorities in Chile have arrested a police officer who allegedly threw a teen-ager from a bridge into a river bed during a protest.

The 16-year-old boy was in stable condition with head trauma and a wrist fracture following the incident in Santiago, Chile’s capital, on Friday. Dozens of people protested on Saturday outside the clinic where he is being treated, condemning police and carrying signs that said: ″He did not fall, they threw him.”

The incident raised more concerns about police conduct since protests about a wide range of social and economic problems erupted in Chile a year ago. Some 31 people have died in the unrest and numerous allegations of human rights violations were filed against police.

The North Central Prosecutor’s Office of Santiago accused the police officer of “causing” the youth to fall and said attempted murder charges would be filed on Sunday.

However, Enrique Monrás, chief of police in Santiago’s western area, said the youth had lost his balance and fallen over the bridge railing after the police attempted to arrest him. Ambulances were summoned so that they could provide prompt assistance, Monrás said.

The government said in a statement that it condemns any violation of human rights. It said a police officer who “does not comply with the protocols or the law” must be investigated and tried in the courts.