He had a long history of violence and alcohol abuse, possibly suggesting he suffered from mental illness. Despite potentially possessing mental illness, he passed on his genes to Angela and her brother anyway, probably leading Angela to suffer from mental illness as well. He sexually and physically abused Angela throughout her entire life, which eventually drove her to kill him.
After Angela finished high school, she ran away from home but was found and brought back by her father.
A newspaper article found in the labyrinth reveals that Thomas was murdered around midnight. Angela was the murderer, who stabbed him multiple times in his neck and left side of torso in a fit of passion with a knife.
A photo left in Room 109 of Blue Creek Apartments in which Angela was residing shows a mother, daughter, father and son in that order. The photo is torn in half between the father and daughter. This could have been done by Angela, showing that the abuse happened when she was young. It is possible that he is Thomas.
In the creased photo, the father appears to look young himself, wearing a checkered shirt. He has what looks to be a five o'clock shadow and short brown hair, while his eye color is not clear. It is possible that the creased form of the photo symbolizes Angela's view on her family as "broken".