Hong Kong police confirmed they fired 55 canisters of tear gas, five rubber bullets and 24 sponge grenades at anti-extradition bill protesters who retreated to Sheung Wan after demonstrating outside the Liaison Office on Sunday night.

John Tse Chun-chung, chief superintendent of the police force’s public relations branch, said on Thursday at a press conference that officers “had no option but to use force” after protesters threw gas bombs, bricks, and umbrellas at the officers.

After a massive march from Causeway Bay to Wan Chai on Sunday afternoon, some anti-extradition bill protesters continued marching to Sheung Wan and Sai Wan and held a protest in the front of the Liaison Office building in Sai Wan. Between 7 and 8pm, protesters threw eggs at the building, sprayed graffiti on walls and defaced the national emblem with black paint. Riot police then arrived with long shields and batons and began charging towards Sheung Wan.

Video footage taken during the clearance operations shows a riot police officer shooting a sponge grenade at protesters on Connaught Road West from a footbridge above them without any warning at around 10pm. But it is understood that the protesters at that time were retreating and had not confronted officers.

Tse said that as the clashes escalated, the force had issued warnings in a blanket manner since 8pm, including raising flags to broadcast messages asking the protesters to leave the site or else force would be used. He said the blanket warning was aimed at the entire protest site.

Tse said he believed officers saw people below the bridge trying to throw bricks, and the officer was therefore justified in shooting a sponge grenade at a protester below.

He added that when an officer suddenly believes he needs to use force, it might be impossible for him to issue a warning.

Meanwhile, the police said it was not the first time officers had used the “40mm REACT ROUND” sponge grenade, which is a riot control weapon. But the force failed to disclose details about when and where the weapon was last used, Ming Pao Daily reported.

The sponge grenade is a “less-lethal” munition with a minimum engagement range of 10-15 meters and a maximum effective range of 50 meters. But it can cause “serious injury or death” if used incorrectly, according to manufacturer Pacem Defense, the South China Morning Post reported.

Meanwhile, a protester was treated for a head wound that is believed to have been caused by police fire.

According to Apple Daily, Pepe (not his real name) was hit on the back of his head by a police round.

Pepe recalled that after clashes with the police on Sunday night, he lost his helmet. Then at around 10:45pm, after throwing some objects at the police, he turned around to retreat. Then he felt a pain at the back of his head and head a loud “bang” nearby. He walked two more steps and then fell to the ground.

Pepe said at that time that he remained conscious but was in pain. Other protesters helped him leave the area. He refused to go to a public hospital as he was afraid that he would be arrested.

He later went to a private hospital to be treated for a 3 cm-long wound on the back of his head that required four stitches. He was later discharged.

Pepe said he was sure he did not see any warning flag from the police when he was injured.

Wong Ho-yin from Civil Rights Observer said police should target the lower body of the individual being targeted to reduce the potential for injury or death.