Some folks think that letting go pets and other animal lives into the wild is some kind of an act of charity, so this is what happens.
The owner finds it cruel (or cumbersome) to keep his pet tortoise, so he decides to let go of it.
Some cruel (sadist) folks (from the public) are around and sick enough to paint the tortoise's back with toxic commercial paint. The word is a chinese character that connotatively implies an insult.
And by the way, what is this tortoise doing on a beach? The scorching sun fried it so hard that this fella is hiding under the bushes along the edge of sand.
What do you think of the pet owners and those who let go living creatures into the wild (or rather concrete) Singapore?