The US suffered more mass murders in 2019 than any other year on record, according to researchers.
A database compiled by the Associated Press (AP), USA Today and Northeastern University recorded 41 cases and a total of 211 deaths.
Mass murders are defined as four or more people killed in the same incident, excluding the perpetrator.
Among the deadliest in 2019 were the murders of 12 people in Virginia Beach in May and 22 in El Paso in August.
Of the 41 cases in 2019, 33 involved firearms, the researchers said. California had the highest number of mass murders by state, with eight.
Many mass killings in the U.S. fail to make headlines because they involve family feuds, drug deals or gang violence and don't spill over into public spaces, researchers said.
The number of mass killings in the US had increased even as the overall number of homicides fell, said James Densley, a criminologist and professor at Metropolitan State University in Minnesota.
“As a percentage of homicides, these mass killings also account for more deaths,” he told the AP.
Professor Densley said he believed the spike was partly a consequence of an “angry and frustrated era” in US society, but added that crimes tended to occur in waves.
“This seems to be the season of mass shootings,” he said.
Gun ownership rights are enshrined in the US Constitution's Second Amendment, and the rise in mass shootings has done little to push US lawmakers toward gun control reforms.
In August, after the deadly attacks in Dayton, Ohio, and El Paso, Texas, President Donald Trump said there would be “serious discussions” among congressional leaders about “substantial” background checks for gun owners.
But Mr. Trump quietly caved to that commitment, reportedly after one long phone call with Wayne LaPierrethe CEO of the National Rifle Association – a powerful lobbying group that opposes gun control measures.
Speaking to reporters after the call, the president said the U.S. is conducting “very strong background checks right now,” adding that mass shootings are a “mental problem.”
Top Democrats have publicly called for stricter gun control measures.
Earlier this month, presidential candidate and former US Vice President Joe Biden used the seventh anniversary of the Sandy Hook school attack to renew the call for stricter regulations. Biden's plans include a ban on the manufacture and sale of assault weapons and mandatory background checks for all gun sales.
Another Democratic presidential candidate, Elizabeth Warren, outlined plans earlier this year to reduce gun deaths by 80% through a combination of legislation and executive action. Ms. Warren also called for stronger background checks, as well as the ability to revoke licenses for gun dealers who break the law.