“I don’t know whether this explains it entirely, but I do have a strong sense that some part of the explanation is a chill wind blowing through American law enforcement over the last year,” Comey said. “And that wind is surely changing behavior.”

The FBI director’s comments come after a series of high-profile cases of police brutality and alleged racial bias, many of which have been captured on video and spread quickly online, adding pressure to police departments to investigate their own and emboldening activists calling for reforms.

Comey’s remarks also bore a strong resemblance to a theory some law enforcement officials have referred to as the “Ferguson effect” — that increased scrutiny on police departments makes officers less pro-active and increases crime.

“They told me, ‘We feel like we’re under siege and we don’t feel much like getting out of cars,’” Comey said, referring to police officers he’s met.