@BillRM,
No, it isn't a given on it's face. It is a made up statistic. Find me a single statistic showing how many people died driving to a movie theater.
Let's examine your attempt to make a claim. Yes, we can agree there are 30,000 deaths driving. We can also agree that over 3.03 trillion miles are driven in the US.
http://www.wolframalpha.com/input/?i=us+auto+miles+driven+per+year
Now we need to figure out how many miles of that is spent driving to movie theaters. The number of movie tickets sold in the US is 1.27 billion or on average about 4 per person per year.
http://www.the-numbers.com/market/.
25% of moviegoers are under 17.
http://www.mpaa.org/wp-content/uploads/2014/03/2012-Theatrical-Market-Statistics-Report.pdf
Let's for the sake of argument assume 4 people per car trip to the theater and a distance of 10 miles to travel. (Some people walk and some cars have fewer people.) That leaves us with about 31 people might be killed driving to or from the movies based on nothing but mileage. It ignores that most deaths are caused by speed or alcohol impaired driving. . It ignores that most deaths occur on major highways. That leaves us with a handful of deaths traveling to movie theaters. It could well be less than a dozen.
While it is easy to argue there aren't a lot of mass killings at movie theaters, we can't ignore that killings that don't involve mass attacks also happen at movie theaters. I can find 5 gun deaths at movie theaters this year with a quick Google search.
Of course, if we want to play the game of deaths vs location, one would expect with 30,000 gun deaths that a number of them happen at movie theaters. Why would I need evidence?