Why is the Gretna, Louisiana area so murdery, by episodes?

The Gretna area is two towns on the west bank of the Mississippi, Gretna and Marrero, with New Orleans across the water. Gretna was settled in 1836 and first called Mechanicsham. It grew as a station on the river, with railroads running in and out and a ferry across to the city, and German immigrants arrived in numbers. By 2018 it held 17,880 people. Marrero, four miles along the same bank, was a low-income town of roughly 32,000 in 1981.

The two episodes sit close together. One is in September 1979 in Gretna, the other on 20 February 1981 in Marrero, four miles apart, each with a single victim. The count is two separate killings, seventeen months apart, in neighbouring towns, and a modest placing of 121st overall, second in Louisiana.

Both cases begin in ordinary places. One starts in a Gretna home with a babysitter, three drunk adults and two small children. The other starts with a group of young men bar-hopping around Gretna and Marrero. Two murders still place the town above every other Louisiana town but one.