NEW YORK (AP) — Unrelenting bloodshed across the U.S. this year has led to the grimmest of milestones: The deadliest six months of mass killings recorded since at least 2006. From Jan. 1 to June 30, the nation endured 28 mass killings, all but one of which involved guns. The death toll rose just about every week, a constant cycle of violence and grief. A mass killing is defined as an occurrence when four or more people are slain, not including the assailant, within a 24-hour period. The 2023 milestone beat the previous record of 27 mass killings, which was only just set in the second half of 2022.