Though it’s not a renowned high-tech hub, Brazos County, Tex., has become the showroom for what technology can do for police officers, paramedics and firefighters nationwide, through the newly created FirstNet wireless network. When Brazos sheriff’s deputies entered a standoff with an armed man inside his home, they positioned four cars around the building and streamed live video through FirstNet back to their command center from their phones. When firefighters launched a swiftwater rescue recently, they were able to show it in real time through FirstNet to their supervisors. When a man tried to fraudulently register a stolen car, a patrol lieutenant was able to patch into the government center cameras through FirstNet and watch the crime in progress.

“It’s given us some incredible communication,” said Brazos Sheriff Chris Kirk, “that we’ve been able to put to good use. It makes us much more efficient.”

The idea for FirstNet was long in gestation, beginning with the terrorist attacks of Sept. 11, 2001, but has rapidly come to fruition in the year since AT&T won a contract to build it for the federal government. The idea was a dedicated wireless network exclusively for first responders, enabling them to communicate in emergencies on a secure system built to handle massive amounts of data.

Former Boston police commissioner Ed Davis witnessed two major problems of emergency communication firsthand. On 9/11, police helicopters flying over the World Trade Center could see the danger of building collapse but could not reach firefighters inside the towers, who were using a different radio system. And after the Boston Marathon bombing, cellular networks were overwhelmed with traffic, and police could not communicate with each other, Davis said. FirstNet addresses both problems.

Though most people have long used smartphones, public safety lagged behind. Walkie-talkies and land-based dispatch systems remain the dominant communication system for police and fire departments, and though many patrol cruisers and firetrucks have computers, they often cannot perform one-tenth the functions of a smartphone. Officers and firefighters were using their private phones to help them do their jobs, but departments that sign on to FirstNet will provide phones that can be used on the network and eventually will be outfitted with specialized apps.

The government agency was created after 9/11 to devise the interoperability of first responders, and then to enable video, data and text capabilities in addition to voice. In March 2017, FirstNet accepted AT&T’s $40 billion bid to build out the network. The governments of all 50 states and the District of Columbia opted in, and in March of this year, the core network went live. More than 1,000 agencies in 52 states and U.S. territories have signed up, including Boston police and fire and the Texas Department of Public Safety.

Shortly after the core network went live, The Washington Post toured AT&T’s Global Network Operations Center, deep underground on an AT&T campus in Bedminster, N.J. One of AT&T’s big selling points to FirstNet was its ability to monitor the network around the clock, and keep it secure from hackers and running during crises.

“Police are always skeptical about the security of their data,” said Mike Poth, the CEO of FirstNet, formally the First Responder Network Authority. “The separate physical hardware is going to be a much more secure network.”

AT&T already had its global center in place, with dozens of analysts monitoring AT&T networks around the world. Now a separate, smaller group dedicated only to FirstNet has occupied work stations in the operations center. Those workers sit in a vast, hushed room facing gigantic wall monitors, showing not only network traffic but also cable news shows, to respond to breaking weather or other emergencies.

That group will also help provide one of the key selling points of FirstNet to police and fire chiefs: priority and preemption. Though AT&T can use its 20 MHz of newly acquired bandwidth for commercial purposes, when a police officer or firefighter accesses the network, that use takes priority. First responders are able to access FirstNet wherever they travel in the United States. And if the network becomes crowded locally, first responders simply knock nonpublic servants off the network to ensure communications stay open in an emergency.

Early reviews of FirstNet’s interoperability are good. Mike Newburn, communications technology manager for Fairfax County, Va., said that when Fairfax’s Urban Search and Rescue Team went to Houston during Hurricane Harvey last summer, “they didn’t notice any impact on their devices; they weren’t ever knocked out. It helped them.”

One concern that public safety leaders expressed was that the network would not adequately cover rural areas. But Scott Agnew, an assistant vice president of AT&T, said FirstNet will reach 99 percent of the country. And for smaller departments that do not have communications budgets, FirstNet is allowing individuals who are certified first responders to obtain from any of AT&T’s retail stores the SIM cards needed to join the network for their own phones.

There remains a competition for customers, even though all 50 states and the District opted into FirstNet. Individual agencies must decide whether to join, and they can still go with other companies such as Verizon, which did not bid for the FirstNet contract but served 70 percent of the nation’s public safety agencies. Verizon is building its own dedicated public safety network, which it says will complement FirstNet and create a marketplace to drive innovation and cost-cutting.

One thing that smartphones need are apps, and first responders have specialized needs: an app to access criminal records, an app to view building floor plans, an app for commanders to control who can access certain levels of FirstNet. Agnew said a dozen apps have been certified so far, and that AT&T held a “hackathon” that attracted 235 developers.

“There’s a passion for it,” Agnew said. “People were asking, ‘What can they do to help public safety?’”

There are still technologies for FirstNet to conquer. Integrating it into dispatch centers, where call-takers are receiving phone calls but could someday receive video from a member of the public, and then send it to responding units, is a likely possibility. Programmers also are considering how to integrate body-worn cameras into FirstNet, so that officers or firefighters can have their hands free while streaming video back to commanders.

Steve Roderick, a volunteer emergency medical technician and AT&T official, said that when he first arrives on a trauma scene, he’s tasked with stabilizing a patient. “Having the ability to interact with somebody in a life-threatening situation,” by having video streamed through a body-camera-type device, “really allows me to do my job and better alerts the hospital so they can be prepared.”

The ability to share visual information rapidly can be a game-changer. Former Boston commissioner Davis, now a consultant for AT&T, said the Boston Marathon bombing suspects would have been identified perhaps days sooner if police had been able to download and process surveillance video with the speed afforded by FirstNet.

And Chris Sambar, a senior vice president of AT&T, said FirstNet was recently available to officers at a rodeo in a stadium in Houston. On that occasion, a family reported a little girl as missing. Surveillance cameras were available, but the stadium was huge, Sambar said. A photo of the girl was sent to all the first responders in the stadium.

“We found her in five minutes,” Sambar said.