Authorities say he attempted to murder his other two children, ages 10 and 13, before locking himself inside a room where he tried to take his own life.
Mitchell's wife was also at home at the time of the incidents, but she was not hurt.
A detective investigating the case says in the warrant filed Thursday that a mask they found in the house, may have been used or touched by Mitchell at some point. Investigators have taken hair and DNA samples from Mitchell.
The detective also says both kids told him they woke up with something over their faces and actually had to fend off their father.
Other warrants have revealed authorities have seized a mask, a knife, two gloves and an envelope from BB&T addressed to Mitchell from the home.
Instead of the Durham County Jail, Mitchell is being held at Raleigh's Central Prison, because of concern over his attempted suicide and public outrage over the case.