Exactly the same thing happened to me. The time was night and the game was lit my moonlight, I was driving two of my friends north in an old hatchback when we got to this road which was extremely steep and the hatchback had a hard time getting its way up the hill. It slowly chugged along when one of my friends pointed out we were getting chased by a zombie. I looked behind as well and saw in the distance what looked like a zombie because of the way it was strafing stupidly like the zombies do with their shitty path finding, but it was running faster than the car because we were struggling to get up the hill. This thing was about 10 metres behind the car when I realized it had a human skin and had the nametag 'Man'. I thought this was just a glitch and we stopped because we still had 1 seat left. I said, "Hey there, want a ride?" But I got no response. The 'Man' got into the car and didn't say a word. My friends and I just sat and tried addressing him and we kind of just assumed he was a hacker. As the driver though, I noticed that when I scrolled my mousewheel the option "Unload Patients" appeared, clicking it did nothing and I brought this up with my friends and they agreed that they had never seen it before. We all got out of the car and looked at the 'Man' and it appeared he had just keeled over and died. We were all like whaaaaaaaaaaaaaaaaaaaaaaaaat.