There are, sad to say, so many shootings in the United States that you already may have forgotten about this one. Police around the country, however, are unlikely to forget the shooting in Florence, South Carolina, on Wednesday, October 3rd that joined the annals of cop assassinations, along with Dallas, Baton Rouge, Des Moines, and Brooklyn.

The South Carolina case began in total routine. Three Florence County sheriff's deputies went to the home of Frederick Hopkins to interview his adopted son, 28-year-old Seth Hopkins, as part of an investigation into a sexual assault. They phoned ahead to be sure someone inside the home would be expecting them. Arriving with a search warrant, the deputies were greeted by a hail of gunfire. One of the backup officers was shot dead and six others were wounded.

The surprising revelation is that Frederick Hopkins, the shooter, is 74 years old. Occasionally, seniors engage in domestic violence, but public mass shootings? That used to be a rarity. Not anymore. The 2017 congressional baseball shooter, James Hodgkinson, was 66. Stephen Paddock, who killed 58 Las Vegas outdoor concertgoers a year ago was 64. And the suspected pipe-bomb mailer the feds arrested Friday is 56-year-old Cesar Sayoc.

When I looked into the issue of crimes by the aging I found some disturbing data. Baby Boomers are doing more crime—and I mean serious crime, not pilfering some groceries—than any previous group of seniors in at least half a century.

“ The Congressional baseball shooter was 66. The Las Vegas concert shooter was 64. The South Carolina cop killer is 74. ”

We used to say that crime is a young man’s game. To a great extent that is still the case. The most prison-prone population was and is males, ages 20 to 29. The most recent FBI report attributes 57 percent of all murders (where age and gender were known) to males between 17 and 34. But so many Baby Boomers are engaging in violence that we may have to rethink the link between age and aggression.

The Boomers—defined by the Census Bureau as those born between 1946 and 1964—played a big part in the great post-'60s crime tsunami. Between 1960 and 1980 violent crime in the United States soared. The murder rate doubled and the robbery rates more than tripled as the young male population (ages 15 to 24) jumped from under 12 million to 21.4 million.

Analysts were convinced that the two phenomena—the youth bulge and the crime spike—were strongly related. For instance, economist Steven Levitt attributed 22 percent of the violent crime increase to changes in age structure alone.

Of course, this meant that nearly 80 percent of the massive crime boom was due to influences other than the sheer increase in youth, as that generation of young offenders engaged in more violent crime per capita than people their age had in decades.

One of these factors is what we call a contagion effect, where youths copy one another and there’s a tipping point at which the copycat behavior increases exponentially. This can be for good (going to college), for ill (doing drugs), or neutral (changing fashions). Crime, unfortunately, is one of those antisocial behaviors susceptible to the contagion effect. (This may explain why gang violence is so persistent in some cities, such as Chicago, but not others, despite comparable conditions.)

But contagions are less common among older populations, so they are unlikely to explain the violent crime of the now-aging Boomers. Another candidate is the common experience of a generation, especially an experience with profound impact on behavior, such as a major war or deep economic depression. For instance, some criminologists think that military service in World War II altered the life trajectories of young men in a positive way and helped reduce crime in the 1950s.

But which events of the '60s and '70s had a criminogenic impact on the Boomers? The Vietnam War and the violent protests it inspired? The revolution in moral values with its overemphasis on individual free choice? The assassinations of public figures? The urban race riots? Perhaps all of the above together, as part of the breakdown in moral authority sociologists call anomie.

Whatever the explanation, we can say this: Now that they’re all grown up, the scourge of the '60s continue to behave badly.

A recent Justice Department study (PDF) found that while the number of state prison inmates increased 55 percent between 1993 and 2003, the inmate population ages 55 and older mushroomed by 400 percent. In 1991 only 4.3 percent of state and federal inmates were 55+; in 2016 the aging Boomers were 11.3 percent of the prison population, a rise of 163 percent.

Most of these Boomers aged behind bars; they were admitted between 1993 and 2003 when they were 45 to 54 years old. Many were in for violent crimes, such as murder and rape, which accounts for the long prison terms. Nearly two-thirds (65 percent) of the 55+ prisoners had been sentenced for violent crimes, the highest percentage of any age group.

Not only were an outsized share of Boomers engaging in violence before 2003, but that has continued since, steadily adding to the dramatic growth in older inmates, as borne out by the latest FBI arrest figures.

In 2017, over 25,000 Boomers were arrested for the four index crimes of violence (murder/non-negligent manslaughter, robbery, rape and aggravated assault), 6.2 percent of all arrests for these crimes. By contrast, in 1990, only 11,000, or 2 percent of the arrests for these violent crimes were 55 and over. In other words, three times as many Boomers were taken in for violent crimes as older suspects in the past. In 1970, elder arrests for such crimes were 2.8 percent of all such arrests.

What about the near future? When the Boomers pass on to that great correctional facility in the sky, will the next cohort prove to be as violent? Maybe so. In 2017, nearly 11 percent of arrests for crimes of violence fell into the 45 to 54 age bracket, whereas in 1990 that age group was only 4 percent of the arrests, and in 1970 less than 6 percent.

Barry Latzer is Professor Emeritus of Criminal Justice, John Jay College of Criminal Justice, CUNY. His most recent book is The Rise and Fall of Violent Crime in America (Encounter 2016).