Very Wierd: Utah Teacher Murdered In School Parking Lot

A 30 year old mother of 2 Head Start teacher was killed near Salt Lake City, Utah by a 70 year old woman who had a concealed carry permit.
No students were in school at the time, but there were plenty of witnesses. When asked why the old lady killed the teacher, she said she did not know. There is a possibility that they knew each other but no motive was established. http://www.deseretnews.com/article/700005762/Teacher-shot-to-death-in-Millcreek-parking-lot.html
Very weird. How many times has a 30 year old woman been killed by a 70 year old woman? Not too damn often.