The ATT Communications node was probably the primary target of the bomber. Reporting is suggesting that he died in the blast. His motive remains unknown but he probably has a hatred of digital society and struck at a critical node on Christmas Day. The timing of the attack indicates that he probably held religious views of some sort. That he designed the bomb to broadcast warnings indicates that he wanted to limit casualties. He had cameras on the vehicle and could have been broadcasting the event to associates via cell phone up until the explosion. In some respects this is similar to a attack against a power station in Silicon Valley that knocked out power to the giant Silicon Valley Corporations. While these attacks used dissimilar techniques the orientation of the attack is similar. This could be the work of either a cell or individual that shares a common world view with the Silicon Valley attackers. Likely this view can be found on the internet in some forum that the bomber frequented. The attack indicates that the bomber was highly technically qualified and that a search of his home computers and digital devices may not reveal much due to him using counter surveillance counter measures.
The FBI has focused on a possible link between the suspect and 5G conspiracy claims. He was reported by a former coworker to be a skilled technologist.
First net is a emergency operations network dedicated to first responders and law enforcement. In a emergency situation normal civilian calls, text messages and digital data transfers are pushed to lower bands giving priority to law enforcement. It is not a spy network but rather a dedicated law enforcement communications band.
I note that my highly accurate assessment of the Nashville Bomber was performed based upon technical analysis of the bomb used in the event. I have over thirty years of experience in these types of events and supported both the investigation of both the attempted Times Square Bombing and Boston Marathon Bombing