July 16 (UPI) -- New details about the motive of the fatal shooting of two Minnesota lawmakers were revealed when federal prosecutors released a letter allegedly written by accused shooter Vance Boelter. The announcement Tuesday accompanied a statement that Boelter, 57, was indicted by a grand jury on enhanced murder charges tied to the killing of state Rep. Melissa Hortman, a member of the Minnesota Democratic-Farm-Labor party, her husband, Mark, and their dog, Gilbert. The announcement came