‘My gut’s telling me the same thing,’ I said. ‘But we also know that the guy’s smart enough to make sure we won’t be able to prove anything.’

A fire grew in his eyes. ‘If it was up to me I’d do what the scumbag obviously did to that firearms officer, Hugh Wallis. Just lift him off the street and make him disappear.’

There was nothing worse than knowing, or at least strongly suspecting, that someone was guilty of a crime and not being able to do anything about it.

At nine thirty, Drummond started the first briefing of the day. He began by announcing that four detectives, including Janet Dean, had not turned up this morning. Janet was claiming that she had a hospital appointment. The others said they were having to deal with distraught family members.

I was surprised that so many of the team had actually come in. The eyes of everyone in the room were glazed and haunted. It was clear that trauma and exhaustion were taking their toll.

There had been a couple of developments overnight. Forensics had confirmed that the same gun had been used to kill both Dave Prentiss and Marion Nash. And some CCTV footage showed the killer entering and leaving the bookshop. It was poor quality, though, and therefore not very helpful. As we viewed it on the monitors, I felt my blood surge.

Drummond provided a commentary. ‘It’s from a street camera about thirty metres from the shop. You can see the figure in a long dark overcoat and baseball cap walking into shot from across the road. He pauses briefly outside the shop and then goes in. Just two minutes later he comes out and crosses back over the road. Unfortunately there are no cameras covering the other side. The next person to enter the shop discovered the body.’

Drummond then put up a couple of freeze frames showing magnified images of the figure in the overcoat. But they were far too blurry to distinguish any features and it was impossible even to tell if it was a man or a woman.

‘We’re about to release this to the media,’ he said. ‘Maybe we’ll get lucky and it turns out someone saw where this person went.’

Drummond then said he was about to have a meeting with the Commissioner and other senior officers to discuss the latest text message that had come through last night, telling us that any officers assigned to protect us would also be targeted.

‘The situation is going from bad to worse,’ he said. ‘So until it’s decided how we respond to this I don’t want anybody going anywhere by themselves. A list of all the civilians who received the original text has been passed on to uniform who will be contacting them about their individual situations. We’ll do everything we can to make them safe.’