Bill Belichick has reached his boiling point in the Antonio Brown saga ... abruptly ending a press conference after reporters peppered him with Qs about his controversial superstar WR.

The New England Patriots coach faced the media on Friday -- just hours after the NFL opened an investigation into alleged texts Brown sent to a woman accusing him of sexual misconduct in 2017.

Of course, the media wanted answers ... but Belichick told reporters right off the bat he wouldn't be answering any questions about AB. He opened saying, "We take all situations with our team very seriously."

"There's some things we're looking into. But, I'm not going to have any comment on any of the off the field situations or questions on that."

Bill also suggested Brown would be active and playing on Sunday when the Patriots take on the NY Jets.

When Belichick tried to move past the Brown questions, the media stayed focused on the bigger story ... and Bill. Got. Pissed.

"I think I've already addressed this ... we're gonna get ready for the Jets here. Happy to answer any football questions. But, the rest of it ... I'm done with the rest of it."

When a reporter followed that up with another AB question ... Bill got fed up, interrupted him and left the podium.

"That's it. Yep, I'm good. Thank you."

Meanwhile, the NFL is still investigating Brown -- but it's theoretically possible league officials could take action on new text message development before Sunday.