Julie Schenecker, 50, was arrested Jan. 28 on preliminary charges, and the Hillsborough County grand jury formally charged her with two counts of premeditated first-degree murder, which could carry the death penalty if she is convicted.
Her attorney, public defender Robert Frasier, declined to comment. Her arraignment is set for Feb. 16.
The day Schenecker was arrested, her mother had called police from Texas and asked officers to check on her daughter, who had been depressed and complaining about her children, 16-year-old Calyx and 13-year-old Beau.
Records showed that the family had been in counseling and police were called to investigate an abuse claim after Calyx told the counselor that her mom hit her on two occasions.
A search-warrant affidavit filed with the court said two police officers found Schenecker unconscious on the screened back porch of the upscale Tampa home, her white robe covered with dried blood.
The warrant said one officer woke her up and took her inside to talk, while the other went looking for the children.
One of the officers found the covered body of Schenecker's daughter, Calyx, in a bed upstairs, the affidavit said. The body of her son Beau was found in a van in the garage, also covered with a blanket. She told detectives she killed them for being "mouthy."
Laura McElroy, a Tampa Police spokeswoman, said Schenecker referred to a "massacre" in a note officers found in home. It was unclear what Schenecker meant and McElroy would not reveal the context.
Schenecker told detectives she had shot her son twice in the head in the van "for talking back" while she drove him to soccer practice. She said she returned home and killed her daughter with two shots to the head while the girl sat at a computer doing homework. She then apparently moved her to a bed.
Both teens were killed with a .38-caliber pistol, which authorities say Schenecker bought five days earlier.
McElroy said Schenecker's note made reference to a three-day gun waiting period, and how it would "delay the massacre."
Bullets, medication and a Smith & Wesson instruction manual were among the items found in the master bedroom and bathroom upstairs, the document said. It did not specify what type of medication was found.
Funeral services for the two teens were held Tuesday in Fort Worth, Texas. Their father, Parker Schenecker - an Army colonel who was working in the Middle East when his children were killed - told more than 500 mourners that his children were loved.
"Now we all must go forward to honor them with love and respect for each other," he said
Julie Schenecker is being held without bail at the Hillsborough County jail.