NASHVILLE — On Christmas morning, emergency officials in the small Alabama town of Cullman found themselves nearly cut off from the outside world.
Their 911 dispatch center was failing, and a backup system was only partly functioning. Veteran officers were having to teach younger colleagues how to use two-way radios to communicate with each other because their cellphones were not receiving a signal.
Phyllis Little, the director of emergency management in Cullman County, had no internet or landline connection in her office. Her cellphone was also out. “I had lights,” she said, “but I had nothing else.”
The source of the disruption was an explosion 145 miles away in downtown Nashville, set off by a man in a bomb-filled R.V. who pulled up outside an AT&T building that is a central hub linking cellular, internet and cable television services across the region. The bombing reverberated across several states, illuminating the vulnerabilities of our interconnected world and leading investigators to question whether the perpetrator, an information technology specialist who died in the blast, had specifically targeted the building.
The effects were far-reaching.
Flights were grounded at the Nashville airport, and communications systems were disrupted for many law enforcement agencies and hospitals, including Ascension Saint Thomas in Nashville, where doctors and other workers relied on phones using a different provider and slept in the hospital to maintain contact.
“The stress at the hospital level because of Covid alone is significant,” said Dr. Evelio Rodriguez, who leads the hospital’s cardio surgery team, “and then you add this and you add it on a holiday weekend where you don’t have as many people working.”
As internet and cellular service was severed for many across the region, the explosion created a slew of inconveniences: Credit card machines stopped working in stores and restaurants. Streaming movies were out of reach for home viewers. And families kept apart because of the pandemic could not even call each other on the holiday.
“This hit home for us,” said Hugh Odom, a telecommunications expert. “When this happened Christmas morning, all around the Nashville area, we had no 911 service. If someone had a heart attack, or someone was trying to rob your house, or you were in an accident, you couldn’t make a call. You couldn’t get any help.”
AT&T raced to restore service after the Friday morning explosion, with most of it back online by Sunday night. But according to experts and many who lived through the experience, the bombing revealed systemic weaknesses of the connections that have become increasingly essential infrastructure.
“I think what we’re seeing is just how vulnerable they are,” said Colin P. Clarke, a senior research fellow at the Soufan Center, a nonpartisan think tank, and a scholar on terrorism and national security, “and how much disruption can result when they are effectively targeted.”
It is still unclear what motivated Anthony Warner, whom investigators identified as the perpetrator of the bombing, and if he had specifically sought out the transmission site. His only apparent connection to the company is that his father once worked for Southern Bell, which eventually became what is now AT&T.
Mr. Warner drove the R.V. early on Christmas morning to Second Avenue North, a tree-lined row of Victorian-era warehouses among newer buildings. Police officers responding to a report of gunfire came upon the R.V., which was blaring a warning that explosives were in the vehicle and that people should clear the area.
“It does appear that the intent was more destruction than death,” David Rausch, director of the Tennessee Bureau of Investigation, said on NBC’s “Today” show.
He achieved that, with the concussion of the blast causing one building collapse, damaging dozens of others and filling Second Avenue North with debris. Three people were injured but nobody except Mr. Warner was killed.
“This explosion not only put innocent American lives at risk, but also affected the critical infrastructure that is the foundation for so many parts of our daily lives,” Representative Bennie G. Thompson, a Mississippi Democrat and chairman of the House Homeland Security Committee, said in a statement.
AT&T said the building served as a connection point for regional internet services as well as local wireless, internet and video services. Initially, the company was able to maintain services by operating on battery power. But the backup generators were knocked out of service by fire and water damage caused by the explosion.
“Unfortunately, damage to power systems eventually created service disruptions,” the company said in a statement. “Our teams were on the ground immediately and have worked around the clock since the explosion.”
The company added that despite having to work at an active crime scene, it had “nearly all services restored within 48 hours.” AT&T said it had deployed more than 15 temporary cell sites and 23 disaster trailers to the site.
Still, a larger question remains about the vulnerability of such facilities.
“It’s plain-and-simple scary,” said Johnathan Tal, the chief executive of Tal Global, a risk management and security consulting firm in Silicon Valley.
He recalled when his company had offices across from a nondescript building in downtown San Jose that in the 1990s handled as much as an estimated 40 percent of the nation’s internet traffic. Anyone could walk or drive up to the building. “That exposure exists, and it’s been known for years,” Mr. Tal added. “And there’s unfortunately a lot to do that hasn’t been done.”
At the height of the outage, 46 counties in Tennessee had disruptions in 911 call center services, state officials said. As of Tuesday, four counties (Bledsoe, Cannon, Lincoln and Perry), home to about 70,000 people, were still without call center services and were using alternate numbers to route emergency calls.
The outages also affected the Tennessee hotline for reporting child abuse, adult protective services and driver’s license services, among other agencies and programs. Severe disruptions were also reported in Kentucky and Alabama.
Keith Durbin, Nashville’s director of information technology, said that a devastating flood in 2010 forced the city to create some backup systems, but that the proximity of the AT&T hub meant that even some secondary vendors relied on the telecom giant’s backbone.
Russell Gill has spent the past three decades as a state regulator and lawyer for telecom firms in Tennessee. He said that because competing telecommunications companies rent space from AT&T in the Second Avenue switching center, the damage could have been much worse.
“It is crazy to have a networking service center like that facing one of the busiest streets in the United States,” Mr. Gill said, suggesting that it would be better situated in a rural area: “Buy as much land as they can and put it behind as many chain-link fences as they can build and create Fort Knox.”
Lamar Payne, who lives a few blocks from downtown, lost the signal on his phone after 10:30 a.m. on Christmas and started receiving texts again on Sunday evening. “That one building disrupted so much,” he said.
Bryan Stephens’s family generally gathers in a different place each year for Christmas. Last year, it was Chicago. The year before, Destin, Fla. This year, the plan was to celebrate apart. When he tried to call his parents and brother, his phone did not work. “I couldn’t communicate with anyone on Christmas,” he said.
His television service was out so he had to hook his TV to a rabbit-ear antenna. “It just goes to show we rely on this technology way too much,” he said.
Markeith Porter also lost his internet and cell service. He could not call his father and grandmother. Texts to his girlfriend, a co-worker and friends wanting to chat about the Titans football game did not go through.
When his phone service returned on Sunday night, he said, he put out about 15 calls.
“It’s difficult,” he said. “Everybody is used to being on their phone.”
Rick Rojas, Jamie McGee and Steve Cavendish reported from Nashville, and Edmund Lee from New York. Tiffany Hsu contributed reporting from Danville, Calif.