Mayor Eric Adams said Wednesday that social media firms could have flagged worrying behavior from suspected N-train shooter Frank James by alerting law enforcement to his vile online video rants before the terrifying attack.

The 62-year-old posted a string of videos on YouTube which frequently included racist diatribes and in which Adams was singled out and threatened by name. In one, uploaded just a month ago, James said he had “entered the danger zone.”

“We are watching signs around us of those who are leaning toward violent actions and ignoring them,” Adams told CNN during a morning interview.

“I cannot play a song on a social media channel that belongs to someone else without them identifying that. Why aren’t we identifying these dangerous threats,” Hizzoner asked. “Why aren’t we being more proactive instead of waiting for this to happen?”

“There is some responsibility, I think, on social media industries and companies,” he added. “[We] must lean into why we’re watching these postings and these threats every day, and no one is giving an early warning sign to law enforcement.”

Adams made the remarks just hours before James was arrested on the Lower East Side, ending the day-plus long manhunt that erupted after he detonated smoke bombs and shot up a packed subway train in Brooklyn during the Tuesday morning rush hour.

More than two dozen people were wounded in the horrifying attack — though, none were injured fatally, a stroke of luck that officials have chalked up to James’ gun jamming.

YouTube’s parent company — Alphabet, which also owns search engine giant Google — did not immediately return a request for comment.

Additional reporting by Theo Wyat