The killer who knifed to death two French police officials in their home this week, claiming allegiance to the Islamic State group, tracked the couple days before the gruesome murders and uploaded his claim of responsibility on the family computer, a judicial official said on Friday.

As the investigation into the gruesome deaths on Monday advanced, France honored the couple, Commander Jean-Baptiste Salvaing, No. 2 officer in Mureaux, a hardscrabble town west of Paris, and Jessica Schneider, a police administrator in nearby Mantes-la-Jolie, another challenging town for police, reports the Associated Press.

Hundreds of officers convened for a somber ceremony at the prefecture of Versailles, the region where the two had lived and worked. President Francois Hollande, who presided, praised the couple as "two heroes of daily life."