Zahir Zakir Jaffer, the suspect in the brutal killing of the daughter of a former Pakistani diplomat in Islamabad, was completely "sound and in his senses" when arrested from the murder scene, the police officer supervising the investigation of the case said on Thursday.

Noor Mukadam, 27, daughter of Shaukat Mukadam, was found murdered at a residence in the capital's upscale Sector F-7/4 on Tuesday.

A friend of the woman, identified in the FIR as Zahir Zakir, was arrested over his alleged involvement in the murder, with police saying he is the son of "a leading businessman of the country".

While addressing a press conference to address what he said were different claims on social media about the killing, SSP (Investigation) Ataur Rehman was asked about the widely rumoured drug abuse history of the suspect, Zahir.

In response, SSP Rehman said while the drug usage was not the domain of the police investigation, "when we arrested him, he was sound and in his senses. He may have had a past history [of taking drugs] but at least at this time he was completely in his senses."

He emphasised that police were focusing on the suspect's "mental frame of mind" and that initial findings indicated the suspect was completely aware of his actions when he allegedly committed the murder.

Regarding his mental health history, the SSP said the police investigation "has nothing to do with that" and was being pursued from the angle of whether the act was justified or not — "which it completely wasn't".

The senior police officer said the suspect was tied with ropes by some people whom he had attacked after killing Noor, before police arrived at the scene.

Police had initially said the victim was shot at before being “slaughtered”. Another person was also injured in the incident.

But SSP Rehman said while a pistol had been found at the suspect's house, the initial investigation and medical report did not show a firearm injury in the incident. He added that a bullet was stuck in the pistol's chamber at the time it was recovered.

Zahir, who is currently in police custody on remand, is being interrogated, the SSP said, adding that police did not currently have information about whether the suspect had a criminal record in other countries.

Rehman said the servants present in the house at the time of the incident had also been included in the investigation and were being questioned on various points such as the duration for which Noor was present in the suspect's house.

Citing the statement of the servants, the SSP said they had heard the noise of a quarrel between Noor and the suspect. But it needed to be determined whether the servants knew the fight would end up in murder, he added.

"If they really knew that its ultimate result would be a murder then they also fall into vicarious liability and criminal negligence but in case they didn't know what its result would be then we will only hold them responsible as far as their liability goes."

It also needed to be established what exactly transpired during the quarrel that led to the murder, the officer said.

According to SSP Rehman, police had been alerted to the incident by a local resident and immediately reached the crime scene since the police station was "hardly at a distance of 10 minutes" from the house.

He said police had acted swiftly, immediately arresting the suspect and covering the crime scene, while evidence was collected by the forensic science agency. "This way we have made the full effort that not a single piece of evidence is destroyed," he added.

He told the presser that the inspector general of police had visited the victim's family and the crime scene, and that he had constituted a special team for the case — led by SSP Rehman himself.

"The special team was made because this case is very important for us," he said, stressing that police were "standing with the aggrieved family, and getting them every kind of justice is our duty and responsibility".

SSP Rehman said the findings of the police investigation would be based on "solid evidence" whether the suspect gave his statement or not. He vowed that police would get him convicted and sentenced based on the evidence.

Answering a question, Rehman said "whenever someone's brutal murder is carried out then we shouldn't care about the financial position of the culprit even if they are the son of a very influential father."

When asked about reports of other complaints against the suspect on social media, the SSP urged those people to come forward and inform the police.

The grisly murder sparked fresh debate about the safety of women in the federal capital, with the hashtag #JusticeForNoor attracting tens of thousands of tweets.

This was reportedly the third brutal attack on a woman in the country in the past few days.