What should I do about my 2-year old dog being agressive to the 7-month old puppy I brought home?

I just rescued a 7-month old great dane/pit mix from getting put down at a shelter! If I didn't take him, he would have been killed today. I have a 2-year old golden retriever, so the shelter said they must do a meet and greet to be sure the dogs got along. They had to do it without me there because my G.R. might act differently if I was not there(get distracted by me or won't misbehave when I'm there). They told me that my golden retriever was a great dog and he loved the puppy, but at first the puppy was a little unsure of him. After about a minute, the dogs began to play like best friends, so they approved the adoption. The puppy had to get neutered, so I picked him up about 3 hrs. ago. I put him in the crate I just got 4 him. I went to the backyard to see my GR. When he saw the puppy, he immediately jumped up to me and would not let go. I let him in and he began to growl and tried to attack the crated puppy. They were fine tgthr b4 maybe my GR doesnt want him in his territory? Help