How do you solve this serial killer mystery?
The killer uses a different hand gun every time they kill. There method is essentially to approach someone walking alone, at night, and shoot them in the head. The killer then leaves on foot, travelling up to 2 kilometres to a vehicle and drives home. On the way he disposes of the weapon in a deep body of water. For example, the killer may toss the weapon out of the car window as he crosses The Causeway or The Narrows.
The killer works entirely alone. He doesn't take souveniers and doesn't take photographs of his victims. He doesn't stay near the victim and has the sense to avoid the crimescene after the fact.
The only notable aspect of these crimes is that the killer likes to be close to the victim when he shoots them. Yet there is no DNA evidence on the victim, nor is there any CCTV footage. The killer clearly scouts and chooses places where no surveilance is in place. For example, the underpass of Mitchell Freeway at Glendalough Train Station, before reaching either of the car yards in either direction.
Note also, however, that the killer never takes a victim in the same location twice. The first murder takes place as mentioned at the Glendalough underpass, but the second is on a footpath by a main road in Rockingham. The third is on a sidestreet in Kenwick. The fourth, on Plain St in East Perth, not far from the WACA and the WA Police Service headquarters. And so on.
With no weapon, no witnesses, no actual pattern outside the method of killing, how do you start to try to identify such a murderer?