Solomon Shinerock—a lead investigator who helped drive much of the intensive, four-year effort—is no longer as actively involved in the case, according to three people with knowledge of the matter, who all spoke on condition of anonymity.

In recent weeks, Shinerock’s pullback from the team investigating Trump has been conspicuous enough to frustrate some who have been on the prosecutors’ side—and has been noticeable enough to quietly delight lawyers working on the ex-president’s and Trump Organization’s end, sources noted.

Another person familiar with the situation described the current state of the team, which had been investigating Trump, as “gutted” and a “shell” of its former self, even beyond what’s previously been reported. The loss of momentum in this high-profile probe—which some of its former prosecutors believe already produced sufficient evidence to criminally charge Trump—has left several lawyers who’ve worked on the investigation feeling frustrated, and in some cases enraged.