Why is the Largo, Maryland area so murdery, by episodes?

Largo is in Prince George's County, about half an hour from Washington. It is an upper-middle-class suburb of cul-de-sacs, where neighbours judged one another by their lawns and household income ran well above the national figure. The name comes from a plantation sold on in 1745, thought to have taken it from Largo Bay in Scotland.

The Largo area runs along the Washington to Baltimore corridor: six towns, Largo itself, Lothian, Bethesda, McLean, Elkridge and Cape St. Claire, none more than 24 miles from the centre, spread over several counties.

Six episodes, 27 murders, and no episode accounts for more than seven of them. Two episodes account for seven victims each, one in Largo in 2008 and 2009, the other in Bethesda from the 1970s into the 1990s. Elkridge adds six between 1979 and 1989, and the rest arrive in twos and threes. It ranks ninth overall and first in Maryland.