NASHVILLE — After an R.V. packed with explosives detonated in downtown Nashville on Christmas morning, law enforcement officials assured the public that they had repeatedly attempted to follow up on a 2019 tip that the perpetrator, Anthony Q. Warner, had been building bombs in a vehicle parked outside his house.
“Legally, there was nothing else that could have been done,” the Nashville police chief, John Drake, told reporters after the explosion.
But a report released on Wednesday found no documentation of any attempts to reach Mr. Warner after officers knocked on his door and got no response. The report added that the police should have acted more aggressively, keeping closer tabs on Mr. Warner and trying to establish the probable cause needed to search his home. Instead, the case sat open for months, as Mr. Warner stewed in conspiracy theories and plotted the attack.
The report emerged from an inquiry into the police investigation conducted by a panel that included senior officials from the Metropolitan Nashville Police Department and others from outside the agency. The panel concluded that there was “no way to know for sure if the suicide bombing on December 25, 2020, could have been prevented.” Yet it identified ways in which the Police Department had failed to conduct a robust investigation into the earlier warning.
The blast unsettled Nashville, unleashing a wave of destruction in a stretch of downtown with some of the city’s oldest buildings, and caused disruptions to telecommunications across the region.
Many had praised the swift heroism of the police officers who responded to a bizarre sight on an otherwise quiet holiday morning, finding the vehicle with a speaker blaring a warning of an impending blast. The officers quickly cleared people from nearby buildings. No one other than Mr. Warner, 63, died in the explosion, and there were no serious injuries.
Yet the Police Department began drawing scrutiny as an incident report surfaced showing that a friend of Mr. Warner’s had called the police in distress more than a year earlier. She had told officers that he was building bombs in the R.V. parked beside his house; her lawyer, who also knew Mr. Warner, told the police that he was capable of building explosives.
The officers went to Mr. Warner’s home in August 2019 and tried to follow up, police officials said, but they had no probable cause to search the home or R.V.
Yet the panel said that the officers should have taken advantage of legal resources available to them to determine probable cause and gone further in pursuing the investigation. Mr. Warner’s friend was in emotional distress and in need of medical treatment at the time of the call, yet the panel said there was “insufficient follow-up” in attempting to learn more from her about the allegations she raised. Police investigators also made no attempt to reach out to Mr. Warner’s employers, family members or neighbors.
The panel also found that the primary officer handling the investigation did not maintain records of his attempts to contact Mr. Warner or his friend after the initial call. The officer told the panel that, at the time of the bombing, “the case was not closed but it was not active,” the report said, adding that the officer also said “cases like that often lay dormant unless another lead or complaint comes in.”
Before the bombing, Mr. Warner, a computer specialist who did freelance I.T. work, displayed to friends a deep distrust of the government and was steeped in outlandish conspiracy theories that had him increasingly unmoored from reality.
He had been particularly gripped by a theory that the earth was controlled by alien reptiles who lived in underground tunnels and could masquerade as humans, which he described in essays that he shared with friends and acquaintances. He regularly camped in a state park west of Nashville where he pursued the alien creatures. “If you try to hunt one, you will find that you are the one being hunted,” he wrote.
Still, months later, the motivation for the bombing has remained shrouded in mystery.
Police officials said on Wednesday that the department was adopting a list of recommendations made by the panel. The department will require far more detailed documentation of how officers follow up on an investigation, noting attempts to call, the number of times officers knock on a suspect’s door or when the suspect is the subject of database checks.
There will also be regular audits of hazardous device case files and meetings with federal and state law enforcement agencies to discuss investigations. The department will also add a more stringent process for classifying a case as inactive.
In a statement on Wednesday, Chief Drake noted the panel’s finding that patrol officers had followed the department’s protocols and procedures and said that the review relied on the benefit of hindsight.
“Deficiencies were identified in the follow-up investigative process,” he said. “It is of paramount importance to all of us that any deficiencies are corrected.”