Complex sentence: In a statement to the HKU community, Tsui admitted that the security arrangements could have been better planned and organized, and apologized to the university's students and alumni for not having been able to prevent the unhappy incident.
Split into simpler sentences: In a statement to the HKU community, Tsui admitted that the security arrangements could have been better planned and organised. He also apologised to the university's students and alumni for not having been able to prevent the unhappy incident.