When a person died a sudden death, his / her original time of death is not yet reached, the soul can't make its way to heaven nor hell. The dead is not given the benefit of a “normal” funeral, but instead, special ritual must be conducted on his / her behalf. It is extremely dangerous to other human beings at the place of unnatural death.
The problem is most people in the world, do not know or don't believe what the Chinese know, as in, the ghosts of the unnatural death, need to seek for substitutes to replace his/ her position at the location of unnatural / violent death.
Another problem is, even if they know, they can't access to the proper prayer rituals to spiritual-transcend (超度) the souls of unnatural death.
There are 3 main types of unnatural death：
1) A person who take his / her own life by commiting suicide
When a person died by commiting suicide, his / her soul cannot enter heaven nor hell, as his actual time of death is not up yet. The hell gate doesn't allow him /her to enter. The spirit of the person is stuck at the same spot of death to repeat the suicide experience again and again.
The ghost will need to lure an unlucky human to die the same manner to replace the ghost (as a substitute), in order for the ghost to move on for reincarnation / rebirth.
2) Death caused by another human being, such as in a murder or an automobile accident
The spot where a fatal car accident has occurred, will likely to be the site of more similar accidents. A person who causes another’s death places himself in grave danger, as the spirit is most likely to seek vengeance, because the soul of the dead died unwillingly. The ghost will need to capture another soul to replace 'it', before 'it' can moves on for reincarnation.
3) Death caused by a malicious spirit
When a ghost causes the death of a human being, it is usually either to seek revenge, or lure a human to die, in order to replace it's position, so that 'it' can move on.
Happened in Singapore
Police Station
On 2 July 2005, a police officer died by playing 'Russian Roullette' with his own revolver in the Yishun North NPC, on the fourth-storey gymnasium. On 16 June 2019, yet another police officer killed himself with a gun shot at the same police station - Yishun North NPC, at the rest area . It took the previous ghost 14 years to find a substitute.
Bedok Reservoir
The reservoir was labelled online as a "suicide destination". saw an unprecedented spate of deaths in 2011 and 2012.
The first death was reported on June 20, 2011, when the decomposed lower half of Chinese national Lin Xiao, 23, was found.
News reports said the apprentice mechanic was depressed after coming to Singapore and had told his mother he would die by jumping into the river.
On Sept 22 that year, the bodies of Madam Tan Sze Sze, 31, and her three-year-old son Jerald Chin, were found floating there. She was said to be distressed over a custody battle with her estranged husband.
Over the next year, at least 5 other bodies were reported to have been found in the reservoir.
Surprisingly, the government took the initiative to engage spiritual service to do spiritual-cleansing at the haunted spot. Representatives from the Inter- Religious Organisation held a prayer session at the reservoir in 2011, requested by former foreign minister George Yeo, who was a Member of Parliament for the area.
Many other haunted places:
There are many more haunted places in Singapore that have similar deaths happening at several locations. Keep track on the news and You will notice the patterns, or do Your own research.
Beware of what You say
One man happened to pass by a graveyard and saw a photo of a lady on the tombstone. He said "What a beautiful lady, if she was alive I'd wanted her to be my wife". Few days later, he rode his motorcycle on the opposite direction on the road and died in an accident - (Ghost covering eyes - 鬼遮眼). His father went to consult a deity ( in trance of a spirit medium) and was told by the deity that a female ghost had took his life to be her husband. A "Ghost Wedding" Ritual was performed for them.
Becoming haunted and unsolved
Even a genuine Feng Shui Master who is based on classical Feng Shui, yet without the knowledge and skill of Taoist Sorcery, doesn't know how to solve the problems of a haunted house, even if it is a 'Good' Feng Shui location.
In certain countries, especially countries with majority who are Chinese, such as Taiwan and Hong Kong, by law, the previous owners must inform the potential buyers, that the house is haunted by a previous unnatural death (suicide / murder) case.
In Singapore, property agents and home sellers are not bound by law to disclose if a suicidal / murder death has taken place in a home.
In Taiwan and Malaysia, with access to Taoist Spirit Medium Worship, there are deities, during Taoist Spirit Medium Procession, that will proceed to the haunted spots and places to do spiritual-cleansing and capture the spirits.
In Singapore, even with majority Chinese, but by law, there is no "Such Thing", therefore haunted public places are not spiritually-cleansed by spiritual masters nor deities (during trance of Taoist Spirit Mediums). If a 'spiritual-transcending' ritual is done on a particular private premise or public place, it is usually private matter, that the Chinese family members of the unnatural dead, engaged a Taoist Master / Monk to do ritual to capture his / her soul and not to harm the other human beings.
Cheng Huang Ye (城隍爷) - From a Water Ghost to a Deity
'Cheng Huang Ye'(s) are tutelary deities in Chinese folk religion, who protect the people and the affairs of the particular village, town or city of great dimension, and the corresponding afterlife location. There are 5 Levels (五階官) of Cheng Huang(s).
The worshipping of Cheng Huang Ye started during the Tang dynasty. Since the Ming dynasty, Cheng Huang Ye took on the role of a spiritual magistrate. In later era, people also believed that Cheng Huang Ye was being appointed as the Officer for registration of Life and Death in the Mortal World.
When a Chinese person is wrongfully accused of a crime and justice is not settled on human realm, he /she would report to Cheng Huang Ye in the temple to seek justice from the underworld court - 告阴状.
The legend for Cheng Huang Ye is more or less the same, no matter of where he originated from. In order for water ghost to get reincarnated, he needs to find a substitute. One day, this water ghost found a young man as his substitute. But when he sees him, the water ghost knows that this man will become an upright and honest official. Hence he did not take his live but followed him wherever he goes, protecting him.
A few years later, the young man won the top scholar. The emperor deeply appreciates his talent on their first meeting and bestowed drinks to the scholar. Just when the scholar was about to take the first sip, he thought of the water ghost which protects him on his journey. Hence, he took the cup and splash behind the door. Of course, the emperor was angry and demanded for an explanation. The scholar gives his reason and further explains that the water ghost had to hide behind the door as he is naked.
The emperor then took off his cloak and threw it behind the door. The water ghost put on the cloak and shows himself. And because of his loyalty, the emperor bestowed a title to the water ghost. And this appointment became a famous forklore phase - ‘Promotion of the Water Ghost’ (水鬼升城隍).
Conclusion: After reading this article, now You know the reason why ghosts of the haunted places, never move on with their deaths, not that they don't want but because they can't. They need to lure some unlucky human folks to die for them to take over their places, or they need to be rescued by Taoist / Buddhist Spiritual Masters, or Taoist Spirit Mediums, by doing spiritual-transending ritual to free their souls.