For the second time in less than a week someone has driven into a crowd and turned a vehicle into a deadly weapon. It is prompting local law enforcement agencies to consider new strategies to help protect large groups of people.
In central Barcelona on Thursday, a van veered onto a promenade and barreled down a busy walkway, swerving back and forth as it mowed down pedestrians and turned a picturesque tourist destination into a bloody killing zone. Thirteen people were killed and 100 were injured, 15 of them seriously, in what authorities called a terrorist attack.
The incident follows chaos that erupted at white nationalist rally over the weekend in Charlottesville, Virginia. A 32-year-old woman was mowed down by a car as she protested the rally. Two Virginia state troopers also died in the crash of their helicopter, which was monitoring the rally.
In the Bay Area, there has been recent efforts to harden some so-called soft targets. Newly installed pollards at AT&T Park in San Francisco are just one example.
In Fremont, the police department purchased and is now using mobile car barriers. The barriers were used in the city's recent Festival of Arts.
And during the Warriors parade in Oakland, buses and other large vehicles were used to block intersections for security.
"Law enforcement and the intelligence community needs as much and as many tools as they can get to stop this," Retired FBI Agent Rick Smith said.
Smith said police agencies here and abroad are having to be creative about how they prepare for large events and big crowds at popular places.
But the vehicle attack in Charlottesville has introduced a whole new dimension to crowd safety. How do police protect protesters, who are often moving from street to street?
That is something Smith says people in those groups need to plan for.
"Just be aware, this is a possibility," Smith said. "That's a pretty sad commentary of where we are today in this country. But you better be thinking about where you're going and what you're doing."
There are two alt-right protests planned for next weekend -- one in Berkeley and the other in San Francisco.
Berkeley police have yet to return calls on how they are preparing. A San Francisco police spokesperson says the department does not discuss operational plans.