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.
Court documents have revealed investigators learned Mitchell had an extra marital affair and his wife confirmed it during an interview.
It also reveals Durham County detectives have seized two laptop computers, two flash drives and one external hard drive belonging to Mitchell as part of their ongoing investigation.
The items are on their way to a FBI lab in Charlotte instead of the SBI. Federal investigators will try to recover any deleted files and also review web searches on the computers.
Warrants released last week revealed a detective investigating the case said a mask in the family's house may have been used or touched by Mitchell at some point. Investigators have taken hair and DNA samples from Mitchell.
The detective also said Mitchell's older 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 knife, two gloves and an envelope from BB&T addressed to Mitchell from the home.
Detectives tell ABC11 Eyewitness News they can't comment on motive, but they're confident they know exactly what happened.
In the meantime, Mitchell is being held at Raleigh's Central Prison instead of the Durham County Jail, because of concern over his attempted suicide and public outrage over the case.