Chronicle

Seattle teenager Andrew Detmer starts videotaping his life; his mother Karen is dying of cancer and his alcoholic father Richard, a former firefighter, is verbally and physically abusive. At school, Andrew is frequently bullied.
Andrew's cousin Matt Garetty invites him to a party to help him meet people, but Andrew's filming causes an altercation with an attendee and he leaves disappointed. He is persuaded by popular student Steve Montgomery to record something strange that he and Matt have found in the woods. The trio enter a hole in the ground, where they hear a loud strange noise and discover a large glowing blue crystalline object which turns red, and gives them painful nosebleeds. As the crystalline object begins to react violently, the camera cuts out. Weeks later, Andrew, Matt, and Steve record themselves as they display telekinetic abilities, but begin bleeding from their noses when they overexert themselves. They develop a close friendship and begin using their abilities to play pranks, but when Andrew telekinetically pushes a rude motorist off the road and into a river, Matt insists that they restrict the use of their powers, particularly against living things.
When they discover flight abilities, they agree to fly around the world together after graduation. Andrew wants to visit Tibet because of its peaceful nature. Steve encourages him to enter the school talent show to gain popularity. Andrew amazes his fellow students by disguising his powers as an impressive magic act. After the show, Andrew, Matt and Steve celebrate at a house party where Andrew becomes the center of attention. After drinking with his classmate Monica, she and Andrew go upstairs to have sex, but he vomits on her, humiliating themselves.
Andrew becomes increasingly withdrawn and aggressive, culminating when his father Richard attacks him and Andrew uses his powers to overwhelm him. His outburst is so extreme that it inflicts psychically connected nosebleeds on Steve and Matt. While Matt ignores the nosebleed, Steve flies up to Andrew in the middle of a storm and tries to console him. However, Andrew grows increasingly frustrated, and Steve is suddenly struck by a lightning bolt and killed. At Steve's funeral, Matt confronts Andrew about the suspicious circumstances of Steve's death. Andrew denies responsibility to Matt, but he privately begs for forgiveness at Steve's grave.
Andrew grows distant from Matt and again finds himself ostracized at school. After being bullied, he uses his powers to tear teeth out of a bully's mouth. Andrew begins to identify himself as an apex predator, rationalizing that he should not feel guilt for using his powers to hurt those weaker than himself. When his mother's condition deteriorates, Andrew uses his powers to steal money for her medicine. After mugging a local gang, he robs a gas station where he inadvertently causes an explosion that puts him in the hospital with significant burns, and under police investigation. At his bedside, his father informs the unconscious Andrew that his mother has died, and he angrily blames Andrew for her death. As his father is about to strike him, Andrew awakens and the wall of his hospital room explodes.
At a birthday party, Matt experiences a nosebleed and senses Andrew is in trouble. He and his girlfriend, Casey, go to the hospital, where Andrew is floating outside. After saving Richard when Andrew attempts to kill him, Matt confronts his cousin at the Space Needle and tries to reason with him, but Andrew grows hostile and irrational at any perceived attempt to control him. Andrew attacks Matt and the pair fight across the city, crashing through buildings and hurling vehicles. When police shoot Matt in the arm, Andrew throws dozens of police (and their cars) through the air, then uses his powers to destroy the buildings around him, threatening hundreds of lives. Unable to get through to his cousin and left with no other choice, Matt kills Andrew by telekinetically impaling him with a spear from a nearby statue. The police surround Matt, but he flies away.
Later, Matt lands in Tibet with Andrew's camera. Speaking to the camera while addressing Andrew, Matt tearfully vows to use his powers for good and to find out what happened to them in the hole. He positions the camera to view a Tibetan monastery in the distance before flying away, leaving the camera behind.

Question: Who becomes withdrawn and aggressive?
Answer: Andrew