The Nebraska shootings could have been just enough to push an unstable, hate filled person over the edge, and they would like to keep it from becoming a copy cat crime.
Just saying!
I am suspicious of their reasoning too. Why keep the name quiet? Is there more to learn (for the police) by keeping it quiet? Are they looking for accomplices? Are they trying to determine the motive?
Since net postings of a lot of perps have been found by the public soon after names are released, could be they wanna do a thorough search themselves before they let the pajama people do it. What would it look like if they say he had no links to any terrorists & the general public finds evidence to the contrary.