Looks like it was your standard grudge-holding erratic individual:
Authorities on Saturday searched Seagoville storage unit as they focused their investigation into the slayings of the Kaufman County district attorney, his wife and a top prosecutor on a former justice of the peace.
Eric Lyle Williams is now the prime suspect in the murder of District Attorney Mike McLelland, his wife, Cynthia, and Assistant District Attorney Mark Hasse, law enforcement authorities say.
[snip]
Williams was convicted of stealing county equipment last year and sentenced to probation in a case prosecuted by McLelland and Hasse. That case is on appeal. Williams faces another theft charge in a case related to money allegedly misused from a law library fund.
Continue reading News flash: Texas district attorneys NOT murdered by Aryan Brotherhood.