Flower pots were flung along the corridor and two were thrown to the grass patch below.
This drama unfolded on Monday morning at Block 93, Bedok North Avenue 4.
Mr Lu Han Xin, 70, was watching television when he noticed his neighbour, a man in his 30s, returning home.
Soon after, the man came out of his flat topless. He knelt in front of the lift and started screaming.
His mother dragged him back in,, but he subsequently burst out of his unit and started smashing the flower pots at the corridor.