LAKELAND, Fla.—Prosecutors will seek the death penalty for a 33-year-old former Marine accused of massacring a Florida family under the delusion that they were child sex traffickers. In a news release sent Friday, the state attorney’s office said the killings of a Lakeland man, his girlfriend, their baby, and the child’s grandmother were “committed on a cold, calculated and premeditated manner without any pretense of moral or legal justification.” Bryan Riley is accused fatally shooting Justice Gleason, 40; his 33-year-old girlfriend, Theresa Lanham; their baby boy, Jody, who was born in May; and Catherine Delgado, 62, who was Lanham’s mother in their homes on Sept. 5. Gleason’s 11-year-old daughter survived despite several gunshot wounds, officials said. A grand jury’s 22-count indictment was filed Tuesday in Polk County Circuit Court against Riley. Other charges included attempted murder of the 11-year-old girl, along with kidnapping, arson, burglary, and animal cruelty for killing …