The Silent Corner by Dean Koontz (2017) Bantam

Jane Hawk was an FBI agent married to a Full Colonel with a happy life and a son they adored.  Inexplicably one day her husband goes to get something in their bedroom and kills himself.  When she begins to investigate a suspicious rise in unexplained suicides, she gets a threatening phone call.  So she goes underground, first placing her child in the home of a couple who are already off the grid, then she starts hunting these people who are finding a way to control people and convince them to kill themselves.