For 54 hours, policemen in Singapore hunted down a man suspected to be behind the grisly killing of a father and son pair in Kovan.

The man they finally identified as being responsible - a fellow cop.

Late on Friday night, with help from Malaysian police, senior staff sergeant Iskandar Rahmat from Bedok Police Division was finally tracked down in Johor, in a Danga Bay restaurant.

He was extradited and brought to Police Cantonment Complex at 12.15 pm on Saturday. He was wearing a black T-shirt and jeans, and stared straight ahead as photographers surrounded the car he was in.

At a press conference on Saturday morning, Deputy Prime Minister Teo Chee Hean, who is also Home Affairs Minister, said the case was especially troubling as the suspect was a cop.

Iskandar, 34, has been with the police force for 14 years.

At the time of the murders, he was facing internal disciplinary proceedings. This started in January 2013 and he was sent to do backroom, not operations, work, and had no access to firearms. He was said to be in debt and had domestic problems.

It is still unclear how he knew the victims - businessman Tan Boon Sin, 67, and his son Tan Chee Heong, 42, also a businessman.

But what is clear is that in November 2012, the elder Mr Tan had gone to a Bedok police station to report that he had been a victim of theft.

Iskandar was the investigating officer at the time, but he was subsequently reassigned from the case, said the police on Saturday. The case was given to another officer who was already investigating a series of similar thefts.

Police revealed that the elder Mr Tan was the first to be killed in his Hillside Drive home on Wednesday afternoon. He was slashed.

It was reported that prior to going home, he had gone to Certis Cisco Centre in Paya Lebar to withdraw some items from a safe deposit box there.

His son was seen staggering out of the house and collapsing in a pool of blood at about 3.40pm. He had also been slashed, in the neck.

The suspect then drove the older Mr Tan's Toyota Camry. It reversed into the son's body. The car then dragged the body before it was dislodged outside Kovan MRT station 1km away. The driver sped off.

The suspect is said to have abandoned the car, then left for Malaysia on a scooter at 11pm that night - even as his colleagues were still at the two scenes of crime.

Police said his identity was established on Thursday morning after piecing together evidence. Details were not released to the public because there was no threat to public safety. It would also have made his arrest more difficult.

DPM Teo said the suspect's actions - if proven - have tarnished the reputation of the police and he had "abused the trust placed in him, and betrayed his colleagues in the police force who serve faithfully and dutifully".

Commissioner of Police Ng Joo Hee said he could not recall the last time a murder suspect was also a police officer. That the suspect was a cop made the police even more resolved to hunt him down, he said.

"I cannot remember the last time a murder suspect was also a police officer. You may have seen this kind of thing depicted in the movies and on TV, but when it happens for real, it hits you like a freight train," he said.

"When I was first told that the murder suspect could be one of our own, my initial reaction was disbelief, swiftly followed by anger and anguish."

He said he wished there was something the police could do to the victims' family to "lessen their anger and sorrow".

"I know that no amount of commiseration or regret will lessen the hurt. All we can do is to bring the culpable to justice, and to mourn with the rest of Singapore the senseless loss of two innocent lives," he said.