The incident happened early Wednesday at a home on Thistle Trace, which is north of Guess Road off St. Mary's Road in Durham/Hillsborough's Hardscrabble Plantation subdivision.
Deputies say they received a call from inside the home around 12:30 a.m. When they arrived at the scene, they discovered 4-year-old Blake Mitchell not breathing and his father injured. Investigators believe the boy was smothered.
They say he tried to kill his two other two children, ages 10 and 13, before cutting himself.
He remains at Duke Hospital and will be charged with murder and two counts of attempted murder when he is discharged.
Lt. Stan Harris revealed Thursday that there was a mask found at the scene, but won't say if the father was trying to disguise himself or if the mask belonged to one of the children.
"We're going to process and have it re-analyzed, fit into our puzzle," Harris said.
Authorities say the family has not returned to the home in the Hardscrabble Subdivision. They were also too distraught to talk to investigators after the attacks.
Authorities say Mitchell had once worked in the Durham County medical services but had been out of work for about a year.
Meanwhile, court documents show the family's money troubles started in 2005. The family's home was in the process of foreclosing, but investigators haven't said whether that was the motive.