one killer drove nearly ten hours to wreak havoc on shoppers at an el paso, texas, walmart. the other is believed to have murdered his own sister during his deadly attack on the streets of dayton, ohio. between them they killed 29 people within the space of 13 hours and left dozens more fighting for their lives in these two cities. they aren t the first, they won t be the last. but what can we learn about them? what can we learn about the psychology of a killer? mary ellen atula is joining us, a former fbi senior profiler and former fbi special agent. thank you for joining us. among the nine people, the killer in dayton, ohio, killed his own sister. what does that tell you? that s a pretty stunning development in that case. it could suggest that there was also a domestic violence aspect to it. as more information comes out, we ll learn that. but if you just set that aside, this is someone that came heavily armed with lots of ammunition, the vest, so the