Investigators say 54-year-old Omar Duran planted the name and address of a male neighbor with the crude bombs in an effort to break up the man's marriage.
Officials say Duran was so protective of a 34-year-old woman he had befriended that he became obsessed with splitting her up from her new husband.
The three double bags were packed with propane and shrapnel and were left in various locations around St. George dating back to September 2.
The bombs were not equipped to explode, but area residents were still unnerved by the incidents.
"We heard about the packages and stuff, I heard about it a few days ago, and you just never think it's your next-door neighbor," area resident Ray Magnuski said. "That's insane. It's a very, very close-knit, very tight community."
Duran is charged with placing a false bomb, criminal possession of a weapon and reckless endangerment.