Wrong way driver on 495 yesterday

I was driving on 495 from VA back into MD coming home from work, close to the River Rd exit. All of a sudden there’s a car in my lane driving at full speed towards me going the wrong direction. Luckily I reacted fast enough that I merged left and we did not collide head on. But I’ve been so shaken and worried - does anyone know what happened? There’s no way this driver didn’t crash into someone or something.