Feeling the Loss

https://well.blogs.nytimes.com/2010/04/21/mourning-the-death-of-a-pet/?mcubz=3

http://www.humanesociety.org/animals/resources/tips/coping_with_pet_death.html

https://blogs.psychcentral.com/always-learning/2010/04/when-a-beloved-pet-passes-away/

Other pets

Surviving pets may whimper, refuse to eat or drink, and suffer lethargy, especially if they had a close bond with the deceased pet. Even if they were not the best of friends, the changing circumstances and your emotional state may distress them. (However, if your remaining pets continue to act out of sorts, there could actually be a medical problem that requires your veterinarian's attention.)

Give surviving pets lots of TLC and try to maintain a normal routine. It's good for them and for you.
Getting another pet

Rushing into this decision isn't fair to you or your new pet. Each animal has their own unique personality and a new animal cannot replace the one you lost. You'll know when the time is right to adopt a new pet after giving yourself time to grieve, considering whether you're ready, and paying close attention to your feelings.

When you're ready, remember that your local animal shelter or rescue is a great place to find your next special friend.