What does it mean when a man looks down and doesn't smile when talking about his engagement?

I'm an assitant coach with two other coaches. There both very young around 20 to 25 years of age. One of them is engaged and today he brought his fiancee to practice she was not introduced of course as co-workers we know she was the fiancee. But his behavior startled me. There is this girl on the team that seems to have attract especial attention to the engaged coach , he always helps her when she struggles but I've always noticed a connection. No to mention , they have the same likes and I could almost say they are the same person its the scariest thing I've ever seen. Two people of different ages with such similar personalities.Anyways the fiancee sat on the side and watched practice and suddenly we go to this ice breaker where the other assitant coach points out that our co-worker is engaged ! so everyone claps , and I turned to look at this coach he looks down and doesn't say anything not even a smile. Then I look at the girl and she's smiling and clapping but she looks pist more than anything. What are you thoughts on this behavior? Is it normal coming from this coach? Is the girl normal as well? what should I do? Does it mean anything that he looked down when they talked about his engagement?