CANTON, Ohio -- The arraignment has been set for 9 a.m. Wednesday morning for a man charged with killing his ex-mother-in-law and his two children.

James Mammone, 35, was charged with three counts of aggravated murder and one count of aggravated burglary. His bond was set at $15 million.

He is accused of killing his children Macy Mammone, 5, and James Mammone, 3. Margaret Eakin, 57, was found in the 300 block of Poplar Avenue Northwest. Eakin is the children's maternal grandmother.

Police said the children's throats were slashed. The children were found in their car seats in a family vehicle in front of an apartment complex on Fulton Road.

Police are not saying when the children were killed, by Mammone's neighbors said the saw them alive as late a 9 p.m. Sunday.

Eakin watched the children while Marcia Mammone, the children's mother, worked. The couple divorced in April.

Police said James Mammone dropped off and picked up the children at their grandmother's, an arrangement that was in accordance with Mammone's visitation rights.

He was not allowed to see the children's mother in person after threatening to kill her before the divorce.

Police said James Mammone made threats to Marcia saying, "I am going to put you in your grave."

He was charged on domestic violence charges about a year ago and given two years of probation in connection with that case.

Police were called to Poplar Avenue after a neighbor heard gunshots.

Some neighbors told NewsChannel5 that nothing about James Mammone's behavior indicated that he could be capable of doing something like this.

"It's overwhelming," said Carol Schering, a neighbor. "It really is that someone could possibly be that screwed up to take their own children and the grandma."

Police are not offering a motive at this time.

This is the city's second triple homicide in recent weeks.

Edward Martino III, 24, was arrested at the end of May without incident at a train station by New Mexico State Police and the FBI.

The victims in that shooting were cousins, 32-year-old Jonathon Pierce of Canton and 22-year-old De'Andre Ruffin of Massillon, and a companion, 31-year-old Melissa Pinney of Canton. They were killed outside the White Crown Café at Ninth Street and Claredon Avenue Southwest.