He had just left work and was about to reach his Bedok home when he received a chilling call from one of his subordinates.
The former senior police officer was told a Singapore Airlines (SIA) plane had been hijacked at Changi Airport.
It was March 26, 1991, and the flight involved - SQ117.
It was the first time an SIA plane had been hijacked.
Mr Raymond Han, who was the officer-in-charge of the police radio division between 1991 and 1999, immediately made a U-turn in his car and rushed back to his office at the former Combined Operations Room (fCOR) at Pearl's Hill Terrace near Chinatown.
Mr Han, now 69, was one of the many officers who had once worked at the fCOR - the nerve centre where major crises were managed and resolved.
To pay tribute to these pioneers, the Ministry of Home Affairs is working together with the National Heritage Board and the Singapore Police Force to organise the Home Team SG50 exhibition at the fCOR.
Mr Han, a grandfather of two, is now the managing director of security solutions company Rayocam. He said the operations room was bustling with activity by the time he reached it.
Speaking to The New Paper at the fCOR last Friday, he said: "We worked non-stop for many hours gathering information on the situation before sending them over to the other officers at the airport.
"We continued working even after the four hijackers were shot dead hours later."
Mr Han told TNP that the operations fCOR changed from a manual system to a computerised one in the early 1990s.
The technology used before this transition was not elaborate, said Mr Cheong Kim Seng, who was the officer-in-charge of the police combined operations room and worked there between 1962 and 1971.
The 82-year-old grandfather of five said calls came in via a manual telephone switchboard. And to send messages, officers used teleprinter machines that looked like typewriters.
He said these devices also acted like fax machines.
He smiled and said: "We didn't have the Internet, no e-mails, no mobile phones and we still managed to get things done."
The former Superintendent of Police also said back then, Singapore had many kampungs in remote places and without devices like global positioning systems, at times it was difficult for officers to find incident sites.
He said: "To tackle this, we would ask the caller to wait for us at a familiar landmark. Then he or she would take us to the scene."
Madam Lilian Lee, now 75, who worked at the fCOR between 1967 and 1977 and operated the switchboard, recalled an incident on the seventh month of the Chinese lunar calender.
A little boy got badly burnt after his clothes caught fire while he was playing near some offerings.
The former sergeant, who has a 12-year-old grandson, said: "Many people called 999 about the incident, but our officers could not find the house which was in a kampung in Sembawang. Back then, there were many places that could not be reached by cars, only bicycles."
When they finally reached him, officers found the boy's entire body badly burnt.
Madam Lee said: "I was already a mother then. If I had seen him, I would have surely cried. But I don't know what happened to him after that."
Madam Lee, who worked eight-hour shifts six days a week, also said female operators often received obscene calls from the public.
She said: "I used to get angry at first, but I soon got used to it and would just hang up."
About the exhibition
It first opened in 1956 and was built like a bunker with thick walls and narrow corridors.
These were made to withstand a direct hit from a 500-pound bomb and to prevent mob incursions.
The former Combined Operations Room (fCOR), located at Pearl's Hill Terrace near Chinatown, is a historical structure of the Singapore Police Force.
It was where major crises were managed and resolved.
They include Konfrontasi in 1965 and the racial riots four years later.
The Home Team SG50 exhibition at the fCOR recreates the 1950s settings and furnishing of the fCOR.
In 2001, the COR moved to New Phoenix Park at Irrawaddy Road off Balestier Road.
The exhibition starts today and will end on Jan 31, next year.
The exhibition is open to the public from Tuesdays until Sundays and admission is free.
This article was first published on October 20, 2015.
Get The New Paper for more stories.