"Even when the last interaction was positive, there can be regret that the last interaction may feel incomplete," Moore-Lobban says. "Of course, there can also be sadness and anger as a response to sudden loss. Both of those can be connected to a need to make sense of something that may feel nonsensical."
And don't underestimate shock.
"Based on the literature, we see that the more common emotions experienced when someone dies suddenly are sadness, anger, shock and surprise," says Jonathan Singer, director, Grief and Responses to Illness into Late Life Lab at Texas Tech University. "These emotions can then lead to other experiences, such as yearning for the person who has passed away."