The shooting started with a routine traffic stop, but the West Texas perp had been on a “downward spiral” long before. The FBI briefed the media yesterday on the history behind the spree that killed seven people in Odessa and Midland. His employer had fired him that day and tried to warn police that the shooter might get violent:

A west Texas man, on a “downward spiral,” made “rambling” calls to police and the FBI before embarking on a shooting spree that took the lives of seven innocent bystanders, authorities said Monday. …

“Right after that firing he called 911 … and so did his employer,” Odessa police chief Michael Gerke told reporters. “And basically they were complaining at each other because they had a disagreement over that firing.”

He left his trucking business employer’s office before police showed up.

By that time, it was too late — the man had already left. However, he himself called the FBI’s tip line and left a rambling, confused message. The traffic stop was unrelated to either of those calls, but it touched off the man’s violent ambitions. It took more than two hours to track him down in front of a movie theater and kill him to end the mass-murder spree.

The FBI has not reached a formal conclusion in the case, but it sounds as though they are leaning toward mental illness as the prime factor:

While the FBI and police stopped well short of explaining the killer’s motive, they painted a picture of a man who’d been struggling for a long period of time.

“It’s a very strange residence. It’s very small. I can tell you the conditions reflect what we believe his mental state was going into this,” Combs said.

“He was a long spiral of going down. He didn’t wake up Saturday morning and walk into his company and then it happened. He went to that company in trouble, probably been in trouble for a while … we really need the public’s help to reach out to us when they see people in that downward spiral that may be on that road to violence.”

Mental illness appears to be the connecting factor in all of these shootings — that, and maybe contagion as a contributing factor. One thing that wasn’t a contributing factor was a hole in the background-check process, according to Texas governor Greg Abbott. The shooter had been denied a firearms purchase after he failed a background check a few years ago:

Texas Gov. Greg Abbott (R) 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.

This will lead to a question that has repeatedly arisen in the background-check debate. Did anyone follow up to prosecute Ator for attempting to illegally purchase a firearm? In the current system, those follow-up investigations are exceedingly rare even though it is a crime for prohibited people to attempt to purchase a firearm by any means. Rather than expand background checks, opponents argue, law enforcement should start by enforcing that existing law first. At the very least, that might uncover the mentally unstable long before they begin shooting sprees.