Texas A&M University quarantined Taylor County (Abilene) in 1999 as having AHB (the so-called, 'Killer bees'). Current recommendations for public safety includes reporting and having the nest of any feral colony removed or destroyed. Your neighbor is wise not to mow in the area of this hive. Even if this hive is presently of European linage, the odds of it remaining so are pretty remote. As best I recall, I believe there were three people killed by AHB last year in Texas. The first was a fellow felling a tree with a chainsaw in east Texas, the second was a guy mowing in the Galveston/Free Port area and the third fellow, just south of Dallas (I don't recall what he was doing...maybe mowing too (?). These were all confirmed AHB kills - if there were other deaths due to AHB, I don't recall reading about them. When AHB are individually out foraging (such as, for water), they're not likely to be aggressive. However a disturbance in their immediate nest area is very likely to set them off. Where they've taken over a "managed" hive, something as simple as a shadow passing over the hive's entrance can bring them boiling out of the hive. The safe thing in your neighbor's situation (your case), would be to get a beekeeper in there (or even, pest control) and get them gone.