PS3-Call of Duty Black OPS Question?

I have now watched the YouTube video of the how the level is finished which is the level that requires you to make your way to the roof-top in Korea and then jump off the ledge and into the room across the street. In the video when he makes the jump and crashes into the room, the doctor is in the room too and then the level continues. I can currently make it to the rooftop and jump over into the next building but the doctor is not in the room with us like it shows on the YouTube video. Have I missed something in this level? There is no doctor with me at all. Maybe I ran through the level too quickly and accidently left the doctor behind but will he eventually catch up and jump through the window if I stand there in the room long enough or do I have to restart this level and make sure I stay with the doctor at all times. I dont even know at what point I lost the doctor, I mean can he be killed? I just dont know what to do and it's getting very frustrating!