meghan hoyer is a data reporter and she joins us now. meghan welcome. >> thank you about. >> define what you mean by mass killing. >> a mass killing is basically four or more dead not including the shooter. and that's the fbi's original definition. woodruff: so technically what happened last night in louisiana wouldn't be considered a mass killing? >> that might be considered a mass shooting not a mass killing. we are interested in the four or more dead. woodruff: what have you learned about the people who do those shoots, who are they? >> sure. they're overwhelmingly male. 97% of the cases they're men. their average age is about 30 but it really ranges. we had teenagers to older adults. men tend to use more guns. women tend to kill this other ways. arson, drownings things like that. woodruff: and what did you learn about the circumstances? about who the victims are, how these things -- or is there a pattern? >> there's not necessarily a pattern but there are certain things that stand out. more than 50% are family-related. so -- and in -