Police investigating the attack which left Shane Gilmer dead and Laura Sugden needing life-saving treatment found ladders used by Anthony Lawrence to get into their home in Southburn near Driffield via a shared loftspace.
He’d knocked down a dividing wall in the loft and removed a hallway light bulb before lying in wait for their return on the evening of January 12 2018.
Before shooting Ms Sugden in the head, he told her he’d been listening to them for a year - which was later apparently confirmed by the police's discovery of a listening device with a microphone fixed to his living room wall.
Mr Gilmer was fatally injured with a crossbow bolt penetrating his arm and body, and into his spine, and died later in hospital.
As well as finding three crossbows, police discovered darts on Lawrence’s kitchen table and evidence of him “making them even more lethal than they would have been” an inquest in Hull heard on Wednesday.
A manhunt ensued and Lawrence’s body was found in a hired camper van on a rural road near East Ayton on the North Yorkshire Moors. He had taken an overdose of the painkiller tramadol.
A jury at the inquest heard that had Lawrence lived he would have been charged with the murder of Mr Gilmer and the attempted murder of Ms Sugden.
Expert analysis found DNA evidence connecting blood stains on the Crocs, Craghoppers trousers and polo shirt worn by Lawrence matching that of his victims.
The heavy bloodstaining on the shoes indicated he'd stepped in or on an area of blood.
Det Sgt Julian Gibbs said: “Given the overwhelming evidence he would have been likely found guilty of both horrendous offences.”
The day before the attack Lawrence gave his sister his dog to look after saying he was going to live in Thailand. However there was no evidence he’d bought a ticket.
The detective said the attack coincided with Ms Sugden’s daughter being away from home but the “significance of that could not be quantified”.
Ms Sugden had complained to their landlord about the smell of cannabis coming into the daughter’s bedroom and the investigation found “clear evidence” it had been grown there.
Lawrence had been given notice to vacate the property the following month.
Det Sgt Gibbs said there were two schools of thought as to why he hired a campervan, one theory being that it would allow him to create an elaborate alibi.
He had also disconnected his phone from the network on the afternoon of January 12, potentially frustrating attempts to place him at the scene of the attack.
While he left his wallet, driving licence and bank card behind, he had “the presence of mind” to take the painkillers suggesting he may have planned for “an alternative outcome”.
The detective said none of Lawrence's family were aware of him possessing the crossbows.
He said: "All the indications were that Tony Lawrence was a loner. We couldn't establish any immediate circle of friends that he would associate with and we concluded in relation to the knowledge of what would take place that only Tony was involved or had the knowledge of what was going to happen."
The inquest continues.