What motivated them? As usual, the Christian hating leftist media is completely clueless.
The media hope that this would turn out to be some disaffected white male were engaged in serious wishful thinking. Disgruntled “lone wolf” white guys have typically been behind mass shootings, particularly school shootings, and almost always end up killing themselves before capture. This type of bombing is the MO of jihadists who, contrary to the media spin, are not always engaged in suicide missions. There are hundreds of dead American and NATO soldiers who died at the hand of IEDs which did not involve a suicide attack. Chris Matthews and his ilk were hoping, beyond hope that this was some card carrying NRA member and were so blinded by their hatred of middle America that they were incapable of making a rational assessment of the facts.