It was a nice chat, it seemed. Only after a bomb exploded on Christmas morning in downtown Nashville could Rick Laude understand the sinister sense behind his neighbor's smiling joke that he will never be forgotten by the city and the rest of the world.

Laude told The Associated Press that when he heard that his 63-year-old neighbor, Anthony Quinn Warner, was identified by the authorities as the man who exploded a bomb that killed himself, wounded three other people, and destroyed hundreds of houses, he was speechless.

Laude said that less than a week before Christmas, he saw Warner standing by his mailbox and pulled over to speak in his car. After asking how Warner's elderly mother was doing, Laude said he casually asked, "Is there anything good for Christmas for Santa to bring you?" 

Warner grinned and said, "Oh, yeah, Nashville and the world anever going to forget me," Laude remembered.

He did not think anything of the comment, Laude said, and figured Warner just meant that "something good" was going to happen financially to him.

"Nothing raised any red flags about this guy," Laude said. "He just kept quiet."

Laude said that when he and other neighbors waved to him, Warner often did not respond, but said he did not take it personally. He said, "I knew that he was just a recluse."

Warner left behind clues that show that he wanted to kill himself and planned the bombing, but a specific motive remains elusive.

"We're hoping for a response. Sometimes, it just isn't possible," said David Rausch, the head of the Tennessee Bureau of Investigation, in an interview on NBC's Today show on Monday local time. "Talking to the perpetrator is the best way to find a motive. In this situation, we will not be able to do so."

Investigators examine the belongings of Warner, including a computer and a portable storage disk, collected during the investigation, and continue to question witnesses as they attempt to find a reason for the blast. An official who was not allowed to talk said a study of his financial transactions had revealed purchases of possible bomb-making materials.

Recently, Warner gave away a vehicle and told the person he gave it to that he was diagnosed with cancer, although it is unknown whether he really had cancer, the official said. To fit Warner's DNA, investigators used some objects retrieved from the car, including a hat and gloves, and DNA was taken from one of his family members.

Apparently, Warner even gave away his home in Antioch, a suburb of Nashville, to a woman from Los Angeles a month before the bombing. A property record dated November 25 shows that Warner sold the home to the woman in return for no money after living there for three decades. The signature of the woman is not on that paper.

Warner served as a tech consultant for Steve Fridrich, a Nashville real estate agent, who told the AP in a text message that Warner had said he was retiring earlier this month.

Officials said that before Christmas, Warner had not been on their radar. Monday, a law enforcement study released found that the only conviction of Warner was on a marijuana-related offense in 1978.

"It seems that the intention was more destruction than death, but at this point, again, all that is still speculation as we continue our investigation with all our partners," Rausch added.

In addition, authorities have not provided insight into why Warner chose the precise location for the bombing that destroyed an AT&T building and wreaked havoc in many Southern states on mobile phone service and police and hospital communications. By Monday, the firm said the bulk of services for residents and businesses had been restored.

According to a law enforcement official who said investigators were investigating Warner's digital footprint and financial records, forensic experts were analyzing evidence from the blast site to try to locate the components of the bombs as well as information from the US Bomb Data Centre for intelligence and investigative leads.

The official, who was not allowed to discuss an ongoing investigation and spoke to the AP on condition of anonymity, said that a variety of possible leads were investigated by federal agents and many hypotheses were pursued, including the possibility of targeting the AT&T house.

The bombing took place early on a holiday morning, long before traffic was busy on downtown streets. Police responded to a call of shots fired when they heard a reported alarm blaring at the motor home that in 15 minutes a bomb would detonate. Then, for reasons that might never be understood, the audio shifted shortly before the blast to a recording of 1964 hit Downtown by Petula Clark.

In addition to the DNA discovered at the blast site, Tennessee Highway Patrol investigators were able to relate the vehicle identification number retrieved from the wreckage to a Warner-registered motor home, officials said.

On Monday, President-elect Joe Biden called the bombing "a reminder of the destructive power that an individual or a small group can assemble and the need for ongoing vigilance across the board."

President Donald Trump did not publicly comment on the blast, but talked to Governor Bill Lee of Tennessee and, according to the governor's office, provided resources and support.