As a personal injury attorney, I've seen how quickly accidents like this one can happen. The driver of the mini-van was simply doing the best they could to avoid an accident. Sadly, it seems the erratic driving often utilized by drivers avoiding wrecks can also be some of the most dangerous. The truck driver, too, had no choice but to react. This just seems like an unfortunate accident for all involved. Our thoughts are with the victims and their families at this time.
When you're driving on the highway, always try to scan the roadway 10 seconds ahead of where your vehicle is heading. Make sure to leave enough braking distance between you and the vehicles ahead of you - most experts recommend at least two car length's distance. Always be on the lookout for escape paths, should something in your lane cause you potential danger.
You can really never 100 percent prepare yourself for accidents like this one, but by taking the necessary precautions, you can set yourself up for a better reaction.