Sorry to hear about his mate. They can be very flighty birds. Mine used to have 'nightmares' and go crazy at night and not settle down until I turned on the light. There was never a reason for them to get scared!!!
I found that a dim light near the cage at night helped them to not panic...
Don't worry.. Its easy for you to sort this out. I have a female diamond dove that had the same problem. I took her to the vet the first time and it cost me a lot of money, and the vet stressed the poor bird out badly. even making her beak bleed.
So I decided to do it myself next time.. it...