the rumor at the time was that the judge had an inappropriate relationship with the sheriff's under-aged daughter.  the article today says that the daughter number was found in the judges phone. the sheriff tried to call the daughter on his own phone a few times without success; then tried to call the daughter from the the judges phone. it doesn't say what (if anything) was said answering the phone; but the sheriff instantly pulled his gun and started blasting.   i assume he snapped, while also realizing that there was zero chance of a judge ever being convicted
United States