[noun] + に至る [noun] + に至った [verb (dictionary form)] + に至る [verb (dictionary form)] + に至った
に至る means "to reach" a point, a stage or a result, usually at the end of a long process. It follows a noun, or a verb in the dictionary form, and the past にいたった至った is the form you meet most: the process has arrived at its outcome.
The goal takes に, as with any verb of arriving. A verb before に至る stays in the dictionary form, even when the sentence is in the past.
The negative にいたっていない至っていない, often with まだ or いまだ未だ, says the process has not got there yet. News reports use it constantly for an investigation or a negotiation still under way.
に至る belongs to writing, news and formal speech. In conversation the same outcome is になった or ことになった.
These go beyond a process reaching its result.
に至った and に至る can describe a noun: how something came about, or a stretch of time up to the present.
Both are separate grammar points built on the same verb. にいたる至るまで marks the far end of a range, "all the way to". にいたっては至っては picks out the most extreme case in a group.