The young Bucks County couple killed in their Churchville home last week died of multiple stab wounds, the county Coroner's Office said Monday. The rifle shots the killer fired at Christina and Tyler Roy that night came after they were already dead, authorities said.

The Roys, who had purchased their first home on Kitty Knight Drive around the time of their wedding in 2016, were slain on the upper floor on April 30. Their bodies were found by a house painter early last Tuesday.

Autopsies determined the cause of their deaths as "multiple stab and slash wounds." After the initial attack, authorities said, the killer shot them with a rifle that belonged to Tyler Roy.

Despite the violent way in which the Roys were killed, investigators said there was no apparent connection between them and their suspected killer, Daniel Mooney, who died on the day the bodies were found.

"Certainly he chose that house, and we're not sure why he chose that house," First Assistant District Attorney Gregg Shore said Monday. "We have no indication to say that this act was anything but random.

"As far as speculating what was going on in Mooney's mind, it would be disingenuous to try and do that," he added.

Evidence indicates that Mooney slipped into the home through an unlocked door, Shore said. There were signs of a prolonged struggle on the upper floor and that Mooney had remained in the house for an unknown period of time afterward.

Shore said he would have no more to say about the case.

"The only three people who truly know what happened in the house were the three people in the house," he said, and they are dead.

Tyler Roy, a construction estimator, and Christina Roy, a professional photographer, were high school sweethearts described by friends and neighbors as a warm and outgoing couple with successful careers and a bright future. Since their murders, outpourings of grief have flooded social media, and a foundation has been set up in their memory.

Mooney, 26, was found unresponsive near Ruth and Clearfield Streets in Philadelphia's Kensington neighborhood last Tuesday,  according to police. He was pronounced dead at 9:30 p.m. at Temple University Hospital's Episcopal Campus of an accidental drug overdose.

Hours after his death, investigators found the Roys' missing Ford Edge SUV in Northeast Philadelphia with Mooney's cellphone inside. Sources said he had sold the vehicle for a paltry sum, and the new owner cooperated with investigators.

Mooney had long struggled with heroin addiction, according to his former co-workers at Murray's Richboro Market, a six-minute drive from the scene of the murders. He had abandoned and returned to his employment at the store several times over the last decade, and his last stint at the store ended in December, when he quit to attend a rehab facility in Mays Landing, N.J.

When he left Murray's four months ago, he listed his address as his parents' house, across from the Roys' house, employees at Murray's said. Shore told reporters last week that Mooney had not lived at the Kitty Knight Drive address for some time. Hours before he killed the Roys, Mooney was a suspect in another crime, a car theft at a Speedway gas station in Richboro. Investigators believe the incidents are unrelated.

The Roys' family is holding a viewing for relatives and friends Tuesday night at St. Albert the Great Church in Huntingdon Valley. After a Funeral Mass Wednesday, the couple will be buried at Resurrection Cemetery in Bensalem.