US Sets Record for Deadliest , 6 Months of Mass Killings. The United States has experienced the deadliest six months of mass killings since at least 2006. . ‘The Guardian’ reports that the grim milestone was reached after the nation had 28 mass killings between January 1 and June 30. ‘The Guardian’ reports that the grim milestone was reached after the nation had 28 mass killings between January 1 and June 30. 140 people have been killed in mass killings in just 181 days of 2023. . ‘The Guardian’ reports that a mass killing is considered any incident where four or more people are slain within a 24-hour period. Northeastern University, in partnership with the Associated Press and ‘USA Today,’ has been maintaining a database on this kind of violence since 2006. The previous record of 27 mass killings was set just last year in the second half of 2022. On July 4, while the nation celebrated its independence, President Joe Biden released a statement amid a wave of violence. . On July 4, while the nation celebrated its independence, President Joe Biden released a statement amid a wave of violence. . The president called for “meaningful, commonsense” gun control reform, including a ban on assault weapons and making gun manufacturers liable. . The president called for “meaningful, commonsense” gun control reform, including a ban on assault weapons and making gun manufacturers liable. . ‘The Guardian’ reports that the National Rifle Association remains staunchly opposed to regulating firearms. 27 out of the 28 mass killings in the U.S. this year involved firearms.