She also bit the elderly woman's hand and hit her with an abs roller.
No similar cases have been reported in the vicinity or other parts of Singapore, the authorities said.
The deceased are a 39-year-old motorcyclist and his nine-year-old son, who was riding pillion.
The elderly victim was heartbroken after seeing just S$3 left in her bank account.
The victims have been identified as a 39-year-old man and his 9-year-old son.
She allegedly screamed and struck a vehicle when she couldn't figure her way out of the carpark.
He allegedly also beat his wife with a cane when she intervened.
The victim and his wife had moved into a rental flat just two weeks ago.
Dogs there have been abandoned as the land is being reclaimed, feeders said.
More than 10 cats have already fallen victim, a resident said.