"In cold blood" is a faction novel, which means it is fiction based on facts. It tells a story of a horrible murder committed by D.ck Hickock and Perry Smith on Friday 13th 1959 in Holcomb, Kansas. On that night the Clutter family was killed by them.
Truman Capote stumbled across a short article in New York Times and got very intrigued by the story. He was waiting for a long time for a story spin like this.
In his book "In cold blood" Capote prepares his readers for the horrible events that are going to happen. Even the name of the book gives a hint to the reader, so it is known that somebody is going to die.
The perspective of the narration switches back and forth which involves the reader more into the story. When the perspective switches to D.ck and Perry, while Clutters are still alive, it makes the reader wonder when the murder is going to happen. With this literately device Capote plays with his reader building up the tension.
At some degree the author tries to make this horrible event a little bit less shocking for his audience. Capote creates suspense by putting questions in his readers heads like: "When the family is going to die?, How will it happen? What will I feel?".
Capote handles the murder by creating suspense because the reader before starting the book already knows that the family gets killed and the murderers get executed, therefore this book is a test of how you will react to the described events.