Major Dave Humphreys of the PCB Police Department said, "The note reads, 'I am not mad at anyone or depressed. It's only business.'"
Humphreys says investigators also found another note at Merring's Ebro home.
"It appears to me this was a pre-mediated act, and we have other evidence to indicate that. It's almost like a dying declaration. He didn't intend to live past that moment, and that's the reason for the note."
Merring tried to kill himself after fatally shooting his ex-wife's new husband, 66-year-old Richard Medeiros.
Panama City Beach police say Merring never lost consciousness after shooting himself in the head. He is currently in a medically induced coma at Bay Medical Center.
"He's under armed guard 24 hours a day. When he's able to leave the hospital he will be placed in custody and taken to jail and charged with an open count of murder."
Humphreys says Merring shot Medeiros three times.
"One shot passed through his neck, another shot to his head, and one through his shoulder from behind."
Police say they continue to investigate and gather evidence to build their case for the prosecution.
Humphreys did not want to comment on camera about what was written in the other suicide note, but police told the News Herald the note explained what Merring wanted done with his body.