That's Patrick Mahomes' fiancee, Brittany Matthews, detailing an incident Thursday with a "homeless person" in Kansas City ... saying she was so scared, she ran a red light to escape possible danger.

"Guys, I can't even talk about this because I just got so scared out of my mind," Matthews said in a video after the incident.

"Ya know, with homeless people around Kansas City, there's quite a few of them and I always try to give them the benefit of the doubt and be nice to them and wave at them and smile and give stuff if I have it -- but like today, this guy really just messed things up."

Matthews -- who's pregnant -- says she was driving through the plaza with her windows open when a man approached her car.

"He kept coming ... and kept coming ... and so finally he was saying something and I was like 'No thank you.' So, I was like rolling all the windows up and right as I rolled 'em all up he starts beating on my car, beating on my windows right at my dogs and the dogs going ballistic."

"So, I just sped off and ran the red light! I didn't even look to see if anyone was coming or anything but you know what, I made it home and that was scary."

Glad no one was hurt -- but the incident puts a spotlight on a larger issue in K.C. ... homeless shelters and resource centers are struggling to keep up with the need for shelter and aid since the pandemic began.