Chief Executive Donald Tsang Yam-kuen condemned the acid attack on Saturday in Causeway Bay that injured six, including two seriously, as outrageous, but said it was difficult to arrest the perpetrator.
Tsang briefly inspected the scene of the attack at about 11.30am yesterday. He then went up to the roof of the old tenement building from which investigators believe the two bottles were thrown.
Afterwards he said: 'The perpetrator chose a crowded place... It is outrageous. But I understand that it is not easy to catch a perpetrator who throws objects from height.'
He said police had been told to do their best to catch the attacker.
The attack occurred just after 10pm on Saturday in the pedestrian area behind the Sogo department store. Police believe the bottles of corrosive liquid were thrown from a five-storey tenement building at 541-543 Lockhart Road. The seriously injured man and woman remained in Queen Mary Hospital, Pok Fu Lam, in stable condition. Four injured women were released from hospital.
Police believe the acid attack, the seventh in a year but the first on Hong Kong Island, is linked to the three attacks in Mong Kok and will investigate the cases together. The similarities include choosing old buildings above pedestrian areas for an attack on a crowded street.
The first of the acid attacks took place on December 13 last year, when 46 people suffered acid burns in Mong Kok.
Police do not link the latest attack to incidents in Sham Shui Po.
Stanislaus Lai Ding-kee, a criminology instructor at City University, said that if the crimes were committed by the same person, it was obvious that seeing people get hurt excited him. 'He doesn't wish to kill people, but wants a large number of people to get hurt,' he said.
'Similar incidents happened also at peak shopping times and places, so they clearly are planned attacks. Perhaps he was even in the middle of the crowd observing how others suffer.'
Police questioned shopkeepers near the scene yesterday. They asked the owners for their CCTV tapes.
The undersecretary for security, Lai Tung-kwok, said society would not tolerate such attacks.
Responding to calls for 'sky-eye' surveillance cameras to be installed in Causeway Bay's pedestrian area, he said the bureau needed to conduct a study of the area before deciding whether to install them.
Due to blind spots, it may not be possible to cover the whole area, he said.