Seth Aaron Ator opened fire on the troopers with a military-style rifle.

The gunman who killed seven people and injured 23 others during an extended shooting rampage in western Texas on Saturday had been fired that day from his job, and he and his employer had both called police after his termination. But state troopers who pulled him over for a traffic violation before the shooting were unaware that he could pose a threat.

Authorities said Monday that Seth Aaron Ator, 36, had reached out to police and to the FBI after he was let go from Journey Oilfield Services. He and his employer called the Odessa Police Department that morning, police said. When police officers arrived at the company's office, Ator had left.

"Basically, they were complaining on each other" over the firing, Odessa Police Chief Michael Gerke said. Ator did not make threats of violence.

Later in the day, Ator left a "rambling" statement with an FBI tip line but did not make a specific threat, FBI special agent Christopher Combs said during a news conference Monday.

Fifteen minutes after the call to the FBI, state troopers with the Texas Department of Public Safety stopped Ator, who was driving a gold-color sedan, because he didn't signal a turn on the highway.

Ator opened fire on the troopers with a military-style rifle, striking and injuring one of them, while firing through the rear window of his car. Authorities said Monday that he shouldn't have had the gun at all.

Texas Gov. Greg Abbott, a Republican, tweeted Monday that Ator did not go through a background check when obtaining the gun used in the attacks, which were spread across at least 15 crime scenes.

Ator had before failed to pass a check with the National Instant Criminal Background Check System while trying to buy a gun, said John Wester, a Bureau of Alcohol, Tobacco, Firearms and Explosives agent.

Years earlier, Ator had been charged with criminal trespass and evading arrest, according to a public records search. His previous interactions with Odessa police were minor, Gerke said.

FBI investigators completed a search of Ator's property Sunday.

"It's a very strange residence, it is very small," Combs said. The conditions of the property reflected Ator's mental state, the agent said: The gunman was "on a long spiral going down."

Traffic stops, though commonplace, are among the most risky aspects of police work.

"There is no such thing as a routine traffic stop," Gerke said.

Saturday's was an extreme example of how such stops can turn in an instant. After Ator fired at police, he then drove off, continuing to shoot at pedestrians and motorists in a rampage that lasted more than two hours and covered a stretch of more than 10 miles. Ator at one point hijacked a U.S. Postal Service van, killing 29-year-old mail carrier Mary Granados. While police chased him through the city, he shot at people from the white minivan.

Victims ranged in age from 15 to 57, and the wounded included a 17-month-old. Officers shot and killed the gunman outside a movie theater.

"Traffic stops are always unpredictable, and unfortunately this manifested itself in a desperate individual doing some very desperate and tragic things," said Thor Eells, director of the National Tactical Officers Association.

The National Law Enforcement Officers Memorial Fund, a nonprofit group that tracks officer deaths, said four officers were shot and killed during traffic stops in 2018. During the same period, five officers were killed in ambushes.

"Traffic stops remain among the most dangerous interactions that officers face," said Robyn Small, the fund's public relations director. Small said traffic stops are akin in danger to domestic disturbance calls and executing warrants.

What makes traffic stops "inherently dangerous is the unknown," Eells said. A 911 dispatcher might provide information to officers when they respond to calls, but traffic stops are a type of "officer-initiated activity" that lacks the benefit of a dispatcher's knowledge, Eells said.

"They really have little or no information about the occupant of that vehicle, what might have transpired in that person's life right before they contacted them," Eells said. Though officers might run license plate numbers through their mobile computers, it is not normal practice to conduct further checks, in part because the owner of the vehicle might not be the driver, Eells said.

A recent source of uncertainty includes the availability of powerful weapons.

"The way gun laws have evolved over the years, the risk they face in these encounters go up," said Darrel Stephens, a former police chief in Charlotte, North Carolina. "The challenges they have with providing the appropriate response have increased."

Stephen said many police departments supply officers with rifles in their cars - something that in the past was not common practice - but an officer must know they are facing a threat before arming themselves with such weapons. The sidearms worn by police who make traffic stops are generally no match for semiautomatic assault-style rifles.

"There is a disadvantage in that you have a sidearm against a rifle-type weapon, which normally can be fired more accurately over a greater distance," Eells said. Approaching the vehicle as though the occupant might have a firearm is "just the safest way to do it," he said. "It doesn't mean you're less polite."

During motor vehicle stops, an average of nine officers were killed and nearly 6,000 were assaulted each year between 1988 and 1997, per a 2001 study conducted by Alisa Smith, a legal studies professor at the University of Central Florida. Smith and her colleague concluded that stops were not as risky as they appeared when factoring in the sheer volume of stops.

"Although the shooting in Texas is tragic and began during a traffic stop, the limited data on the threat of traffic stops does not demonstrate that they are more dangerous than other interactions," Smith said.

Each day, police pull over about 50,000 motorists, according to the Stanford Open Policing Project database, a project that has probed the increased likelihood, per share of the population, that police will stop black drivers over white drivers.

Chuck Wexler, director of the Police Executive Research Forum, a Washington-based think tank, noted that officers stopped 19 million drivers in 2015.

"Traffic stops are an everyday piece of police work and rarely lead to the kind of violence such as an active shooter situation," Wexler said. He added: "With 300 million guns in this country, police officers approach these situations with a higher degree of care than in most countries."