This is why the government of some countries are working hard to make sure that gambling is banned in their nation because it causes a whole lot of alarming issues. Imagine waking up to such a disturbing news, I'm sure the people in the Philippines were perturbed by this. Gambling shouldn't be something that is supposed to resort to violence. I think they were under the influence of hard drugs
Similarly, many countries have been quite successful in regulating gambling, as it can fundamentally be a source of state revenue. However, without strict oversight, the impact can be devastating, as in the case described by OP.
I can't imagine that these murders only came to light after so many victims had fallen. Perhaps the police in that country were indeed very corrupt and collaborating with the murderers.
Naturally, such a large number of murders would be deeply unsettling to the public. The police should have been able to uncover the truth in that case much sooner.