I was thinking that most murders are gang-related and most gang members are male, but I see that this is disputed. Unfortunately, all the sources I can find seem to take a partisan position in the gun control debate, hence I don't know.
Bad prior. Gang violence is a major murder statistic, but it's pretty far from being "most". Quick googling says: "1 in 6 murders". The most common motive, at 50% is "Argument". So.. men are more likely to escalate those to homocide?
Here are the New York Times, CNN, and NBC. Here is Wikipedia for background.
The case has made several appearances on LessWrong; examples include: