Before a red SUV smashed into parade marchers Sunday in Waukesha, Wisconsin, the driver plowed through barriers and raced past a police officer at a security post.
As horrible as the incident was, the brazenness of the apparent assault is not altogether unusual.
The incident, which left five people dead and at least 40 injured, raises new questions about the best security practices to protect crowds from a proliferating phenomenon known as "vehicle ramming."
Weaponizing of vehicles is a practice sometimes used by terrorists abroad. But the wanton attacks have also surged in the United States. The increase began after the police murder of George Floyd prompted Black Lives Matter demonstrations, which in turn prompted angry or fearful motorists to run over protesters.
A Boston Globe survey identified at least 139 incidents in which vehicles rammed into crowds of demonstrators since Floyd's death in May 2020. Fewer than half resulted in criminal charges.
The ramming in Waukesha does not fit the demonstrator profile: Paradegoers were simply celebrating Christmas, and Police Chief Dan Thompson stressed in a news conference that the carnage was not an act of terrorism. Instead, the driver, identified as Darrell Brooks Jr., allegedly was fleeing the scene of an earlier domestic violence incident when the assault happened.
Police said Monday night that they were drawing up five charges of intentional homicide against Brooks.
Yet the security questions remain. How did the SUV get onto a parade route? What security measures were in place, and were they enough?
At a news conference, Thompson said barricades had been put up at cross streets and police squads were in place to prevent traffic from breaching the parade.
"When the officer tried to engage and stop the threat, (the driver) still continued through to the crowd," Thompson said. The officer fired his gun at the SUV but was not able to thwart the attack.
Video shows the red SUV crunch into and over metal barricades laid end to end on the roadway, then roaring past a police officer.
Waukesha officials could not be reached Monday to discuss security measures in detail, and a copy of their plans was not immediately available.
Participants in the 58th Annual Waukesha Holiday Parade marched down Main Street, through the heart of the community's business district. More than a dozen streets intersected the route.
A Department of Homeland Security web page on vehicle ramming notes that street events and other gatherings provide "soft targets" that often have little protection and can be attacked with "devastating impact."
The DHS guidance says security plans should take into account event needs and venues, so strategies "cannot be a one-size-fits-all approach." Standard precautions include the use of bollards, trucks, planters and other barricades to separate crowds from weaponized vehicles.
"It is important to ensure that these architectural solutions are appropriately sized, adequately anchored, and purposely reinforced against impact loads," the DHS advisory notes.
Mia Bloom, a fellow with Georgia State University's New America's International Security Program, said event planning can help. But in the end, "Securing a venue is virtually impossible" - especially when the crowd is on a street. There are just too many access points, she said, and too many ways to attack.
She noted that the Waukesha driver penetrated security just as a terrorist would: "It wasn't premeditated," she added, "but it wasn't accidental."
Bloom warned that vehicle-ramming incidents are likely to increase because at least 15 states have adopted or are considering laws that shield motorists from criminal charges when they drive into demonstrators.
In an article for Just Security, Bloom said that tactic gained traction among right-wing extremists after neo-Nazi James Fields killed one demonstrator and injured others with his vehicle during a rally in Charlottesville, Virginia, in August 2017. Fields was convicted of murder and sentenced to life in prison.
Today, Bloom said, fringe groups use social media to advocate vehicle attacks, stressing that drivers can simply claim they were fearful and defending themselves against rioters. That legal posture seems to be successful: According to the Globe, of 139 vehicle attacks on political crowds over the past 16 months, fewer than half resulted in criminal charges.
From the mid-1960s until Floyd's death, there were only three such attacks targeting political protests.
Bruce Butterworth, senior transportation researcher with the Mineta Transportation Institute at San Jose State University, said Waukesha's tragedy points the difficulties faced by security planners.
City officials could hardly anticipate such an attack, he noted, and preparations always involve a balance of costs with safety - based in part on intelligence.
Butterworth, who co-wrote a 2019 study titled "Smashing into Crowds," said nearly half of all incidents involve a driver who is mentally unstable. Their behavior is unpredictable, he noted, and often doesn't show up on the intelligence radar used by threat analysts.
Brooks' psychological history is unknown, but The Milwaukee Journal Sentinel, part of the USA TODAY Network, reported that he was recently released from jail while facing several charges stemming from violent incidents.
Butterworth compared a heavy car or truck plowing into pedestrians to a motorized bowling ball mowing down pins. The goal is to "eliminate the bowling alley," he said, or limit lethality by creating barriers and escape route.
Amid attacks by mentally disturbed people and the surge in rammings at political gatherings, Butterworth.
said even small-town officials have a more difficult job devising security for carnivals, parades and rallies.
"The availability of a car as a weapon has now become part of the landscape," he said. "It's not that you can eliminate easy targets, but you can certainly reduce them."
This article originally appeared on USA TODAY: Waukesha impact: Security planners struggle to stop weaponized cars