Thanks to the house owner, we had the door repainted. After that, we put a sign who stays in the house including the phone number. It's been a week after the incident and thank goodness there's no more writings or some funny red paint on the wall or door.
It truly scared out of my wits whether the Ah Long going to burn the apartment down or maybe entered the house and wreck the whole place like what my colleague's friend had experienced(due to the previous tenant as well).
That's the sort of risk when it comes to renting a house. My dad and I should have suspected the last tenant had owed a lot of money because he had so many mails sent by banks for his credit cards. One new note from my friend, even banks are capable to ask Ah Longs to collect debts for them. Geez, this is so lame. Can't they just blacklist the fella, inform to all other banks and detect his place of stay when he reregister for a new account?