It was a violent year in the United States. In total, there were 41 mass killings, which are defined as instances when four or more people are killed, excluding the perpetrator. More than 210 people were left dead in the mass killings, 33 of which were mass shootings, according to a database compiled by the Associated Press, USA Today, and Northeastern University. In a reflection of how common these killings have become, most of them did not make much news nationally.

The number of killings are the highest since the database began tracking them in 2006. But other research dating back to the 1970s shows there was no other year with as many mass killings either.

The highest profile shootings usually involve a gunman opening fire in a crowded place, but that is not a reflection of mass killings as a whole. The majority of the killings involved people who knew each other and the motives behind the killings are often a mystery.

James Densley, a criminologist and professor at Metropolitan State University in Minnesota, pointed out that one factor that makes the increase even more astounding is that it comes at a time when homicides in general are decreasing. “As a percentage of homicides, these mass killings are also accounting for more deaths,” he said.

“What makes this even more exceptional is that mass killings are going up at a time when general homicides, overall homicides, are going down,” Densley said. “As a percentage of homicides, these mass killings are also accounting for more deaths.” Crime usually goes in waves and while earlier decades saw more serial killers, for example, now shootings appear to be the norm. “This seems to be the age of mass shootings,” Densley said.

When mass shootings rather than mass killings are taken into account, the numbers are even more devastating, according to a separate database kept by a gun violence research group. As of December 26, there were 410 mass shootings—defined as any incident in which four people are shot except the shooter—in the United States. That means there were easily more mass shootings than days in 2019, according to data from the nonprofit Gun Violence Archive (GVA). With a few days to go before the end of the year, the number already marks a new high for the database that began in 2013, far ahead of the 382 mass shootings seen in 2016.

This is the highest number (previous high was 382 in 2016) of mass shootings America has witnessed since we began collecting mass shooting data in 2013. https://t.co/7uwDZ1P16F — Gun Violence Archive (@GunDeaths) December 27, 2019