Unrelenting bloodshed across the United States has set the grimmest of milestones in the first half of this year, with 28 mass killings and 140 fatalities, according to a database maintained by The Associated Press and USA Today in partnership with Northeastern University in Boston.

The number marks the deadliest six months of mass killings recorded since at least 2006, and the death toll rose almost every week.

Nearly all the mass killings in the first half of this year, 27 of 28, involved guns. The other was a fire that killed four people in a home in Monroe, Louisiana.

"What a ghastly milestone," said Brent Leatherwood, whose three children were in class at a private Christian school in Nashville, Tennessee, on March 27 when a former student killed three children and three adults. "You never think your family would be a part of a statistic like that."

According to the database that tracks large-scale violence dating back to 2006, a mass killing is defined as when four or more people are murdered, not including the assailant, within a 24-hour period.

The 2023 milestone beat the previous record of 27 mass killings set in the second half of last year. James Alan Fox, a criminology professor at Northeastern University, said he had never imagined records like this when he began overseeing the database about five years ago.

Futile attempts

Mass violence most often spurs attempts to reform gun laws, even if the efforts are almost always unfruitful.

The Nashville shooter used three guns in the attack, including an AR-15-style rifle. It was one of at least four mass killings in the first half of this year involving such a weapon, according to the database.

Despite the carnage, the National Rifle Association opposes stronger controls on firearms, including AR-15-style rifles and similar weapons.

" (President) Joe Biden and (Vice-President) Kamala Harris' constant efforts to gut the Second Amendment will not usher in safety for Americans," NRA spokesman Billy McLaughlin said.

"That is why the NRA continues our fight for self-defense laws. Rest assured, we will never bow, we will never retreat, and we will never apologize for championing the self-defense rights of law-abiding Americans."

The political paralysis surrounding gun policy has prevented the US government from taking meaningful steps to address the problem, according to a report by Fars News Agency of Iran.

The report came as the US was still reeling from three mass shootings that killed 10 people and wounded nearly 40 others around Independence Day on July 4.

Xinhua and agencies contributed to this story.