Microwave works with door open

Question

I have a GE microwave. When I partially open the door (not fully open, just a crack at the top), the microwave will start buzzing. The buzzing stops if I close the door or open it completely. I did not open the door while the microwave is running.Does partially opening the door cause the magnetron to turn on and leak microwaves?(P.S. I think I only disengaged the top switch on the door when I opened up a crack.)