Schizophrenia. Can be brought on or exacerbated by stress, trauma, a blow to the head, alcohol and dug use, biochemical imbalances.
Delusions
Delusions are false beliefs that are unreal to others but the person feels are completely true. Despite logical argument to convince otherwise, delusions are often fixed and unshakeable. For example, the person may believe they are being watched by the FBI, or their food and drink is being poisoned. They can behave in a very paranoid and suspicious manner towards people they normally trust.
Oscar believed he was being followed on several occasions.
Hallucinations
Where the person can hear, see, smell, taste or feel something that is not actually present. For example, they may hear and respond to voices in their head, see and feel insects crawling over their body, or smell and taste things that others do not.
Dreams and smells blood that isn't there.
Changed emotions
The person may experience fluctuations or exaggerations in their feelings, a loss of feeling, or a lack of control over feelings. Emotional expression may seem dampened, flat, or not in keeping with the situation (eg giggling or smiling when expressing sadness). They may generally feel at odds with the environment or themselves, or feel that the world is moving faster or slower than usual.
Well he shows at lot of these!
Changed social behaviours
The person may act very differently than usual, with behaviours often directly relating to their experiencing delusions, hallucinations & changed emotions. Eg:
 Being very active or feeling very lethargic.
 Extreme or incongruent reactions to events and situations (laughing or crying inappropriately, angry
without cause).
 Isolating from family and friends, or withdrawing from usual social and occupational pursuits.
And these!