In fact, anyone that questions this, point out the assassinations in the past in Europe and elsewhere.
It should be assumed that Iran has sleepers, targets, maybe even some pre cached supplies needed to conduct such missions here.
But the conditions for the use of this capability aren't there yet.
I worry about drones.
You can buy a nice fishing drone for about $3000. It can carry 10 pounds of explosive goodness, and it would be easy to have it drop the stuff on a gathering.