STOCKHOLM (AP) — Sweden’s prime minister says a truck crash in Stockholm was an attack on Sweden. It’s the latest in a string of incidents where drivers have used their vehicles as weapons. Some were orchestrated by extremist groups, others by unstable individuals with unclear motives. Radical groups have urged supporters to use any weapons at hand, including cars, a tactic that presents a major challenge for security forces around the world. Here’s a look at some other attacks: {..snip..}