Korryn Gaines believed she had lead poisoning. In black communities, it’s very common.

On Monday, police went to Korryn Gaines’s apartment with an arrest warrant over low-level offenses. The situation ended up escalating out of control: Gaines, a black woman, barricaded herself with a shotgun reportedly aimed at police, with her 5-year-old son at her side. She allegedly threatened police officers. After nearly eight hours, a shootout broke out, and Gaines was shot and killed by police.

For many, the situation has raised a question: Why did she act so erratically instead of surrendering to police?

Well, there’s one possible answer: lead poisoning.

Rachel Weiner and Lynh Bui reported for the Washington Post:

Gaines had a history of problems with anger and impulsive behavior, according to assessments from a doctor included in a lawsuit Gaines filed in 2012 against the owner of two Baltimore rental homes she had lived in as a child.

Her suit alleged “a sea of lead” paint made her ill.

A doctor who examined Gaines found that she continued to display “signs of neurocognitive impairment,” and “lost significant IQ points as a result of that exposure.”

The lawsuit was still pending at the time of Gaines’s death. But if her allegations are true, they could explain her behavior — lead is known to make people, particularly those exposed to lead as kids, more aggressive and erratic.

That would certainly help explain why Gaines reportedly barricaded herself in her apartment, wielding a shotgun against police while threatening to kill them, when officers arrived to arrest her for low-level charges. It would also help explain why she reportedly told police they would have to “murder” her to get her out of a car during a previous traffic stop, leading to a physical struggle as Gaines clung to her children.

There’s a racial element to lead, too. A 2013 study from the Centers for Disease Control and Prevention found that although blood lead levels among US children have dramatically dropped since the late 1990s, average blood lead levels among black children (1 to 5 years old) between 2007 and 2010 were still roughly 38 percent higher than they were among their white peers.

This is a common problem in poor and minority areas in Baltimore, exposing how these kinds of racial disparities in lead poisoning happen. It’s not that there’s a grand conspiracy to contaminate black children with lead. Instead, centuries of discriminatory and oppressive policies have pushed black people into poor neighborhoods, towns, and cities that can’t afford the lead abatement programs that wealthier areas can.

But it has lifetime effects on these communities: Exposure to lead can produce learning disabilities, lower IQs, and impulsivity, on top of erratic and aggressive behavior. The effects are so bad that some researchers believe the drop in blood lead levels in the past few decades may at least partly explain the United States’ massive drop in crime since the 1990s. As the CDC explained in its study, “No safe blood lead level in children has been identified.”

Gaines, then, may have been another victim of an environmental hazard that most hurts black Americans. But in her case, the effects may have cost her her life.