Happened to me once in one the high rise building in Mutiara Damansara.

It was in 2008. That day was my last day in office in that company. As usual i went back late since that time i was single and got no night time activity. It was around 730pm I heard a sound like group of kakak office laughing at a joke. Then i went to check at if anyone is still around since it's already late. To my surprise there was nobody in the office except me. I quickly pack my stuff and went down to the guard control room. Asked the guard if anyone just left the office before i went down. Guard said i was the last to leave. Then i told them about the incident. He said it's quite normal. They always lock the office in pair if everyone left early.