Warning call- re: suspicious vehicle. hmmm
Possible motive to kill first responders by luring them in... blm / antifa- at top of THIS list.
High energy explosive of unknown (large) # of lbs... ROP.
Bombing on Christmas Day / religious holiday... ROP.
BLM, Islam, Antifa team effort? That would be a natural team, a Christmas day religious event to kill police... that works.