Dow Down 416 Points? Why?

China's stock market plunged 9 percent scaring the rest of the world into selling their stocks. This mass selling of stocks caused the stock market to drop 416 points in one day. Dow has lost about $6 Billion in market value which will send their industrial average into the negatives for the rest of the year.
During the Great Depression affected more than the United States. During the Great Depression the stock market crashed and a tremendous amount of people lost most if not all of their money. it took years to get out of the debt.
I plan on buying more stocks because eventually stocks will go back up and increase their values. I think it is a time to buy stocks now that they are cheaper because everyone knows what stocks are always going to make money. Gas and electric cannot stay in a slump for too long because everyone uses them. They should be back up in a little while. in my opinion buying stocks at any time is a risk so it's better to invest in something you are positive will make money.