They were the largest of the dark web market sites, and they gave customers a notice to get their coins out before today, and it caused a sell off in coins. There were 1000's of vendors on there, and if they gave customers a notice, you know they gave the vendors a notice even earlier, so its pretty obvious that people were pulling coins out and selling them as quick as they could unsure of what was going on with their $. This is what the news is reporting anyways.
Another possibility is the rumor that possibly the feds nailed them earlier this month and the feds were running the site tracing coins as they left, who knows, but thats one rumor going around. Dark market sites that shut down are not known for giving notice and letting people get their coins out, like silk road 1 and silk road 2. Anyways my point is that anything can and will cause btc price to move down, Ive yet to see news that moves it up,JMO.
later