So know this: Sometimes, people contemplating suicide warn us, said Dr. Charles Raison, a CNN contributor and an associate professor of psychiatry at the University of Arizona.

"People who kill themselves often will tell someone ahead of time," he wrote for CNN after the suicide of filmmaker Tony Scott. "Any such communications should be taken with utmost seriousness, and all efforts should be made to keep the person safe and get him or her to appropriate treatment immediately."

Nearly every person affected by a murder-suicide anguishes over what they might have missed to prevent it or get someone help, Campbell said.

Joe Linta, Belcher's agent, had trouble finding words to express his feelings.

"You just ... the how and the why ... is the craziness of this," he said. "There was nothing in my relationship with him that would indicate any troubling past, anything that troubled him ..."

"Maybe he knew he had to take his own life after what he had done," the agent wondered.

"We'll never know, unfortunately."