DURHAM -- Testimony resumed Monday in the murder trial of Joseph Mitchell. He's charged with first degree murder for allegedly suffocating his 4-year-old son back in September 2010. He's also charged with two counts of attempted murder for allegedly trying to kill his two older children.

Mitchell's father in law, Peter Perolini, testified Monday. He talked about moving to North Carolina to live with the married couple. Prosecutors also went over crime scene photos with him. The defense played a tape of Perolini and Mitchell's wife being interviewed by detectives. They were visibly angry over the death of Blakel but said the case was "mind-boggling" because Mitchell was a good father and very involved in his lives.

Investigators also took the stand, testifying that when authorities arrived on scene, Mitchell locked himself in a room and stabbed himself several times.

"The defendant was holding the door back. As they continued to try to push the door open, they observed large amounts of blood," said Lt. Anthony Prignano of the Durham County Sheriff's Office.

Investigators also testified about their interview with the two older children who said their father tried to kill them too.

"Devin says he was asleep and he woke up because of his dad's hands were over his mouth. Then his dad put his hands around his throat. Devin said his dad left but it was too dark to see if his dad was still in the room," said Investigator Len Roberts of the Durham County Sheriff's Office.

The prosecution is expected to wrap up its case as early as Tuesday. The case could go to the grand jury as early as this week.