This morning, Buddy was having what sounded like an asthma attack. I remember a women at the dog park saying her little Yorkie has asthma, so I decided to search online. What I found is that Buddy was having a Reverse Sneezing attack.
In a Reverse Sneeze, air is pulled in very rapidly which makes a loud snorting type noise. When a dog is having an attack, he/she usually stands still with the elbows spread apart, head back, and eyes buldging. A Reverse Sneeze can last a few seconds to a couple of minutes.
Because of the sudden scary noise, many owners want to rush their dog to the vet but according to this article that is not necessary unless other symptoms are present or it occurs frequently.
Please see the article below for more information and a video of a dog who is Reverse Sneezing.