gaara is a sacrificed child, condemned before birth to become the carrier of One-Tailed Shukaku, on the orders of Kazekage, his father. Gaara's mother died a sacrifice during this process, but before death she cursed his father in hope that Gaara be their weapon of own destruction and for Gaara to "love only yourself, fight for only yourself".
Feared because of the monster locked away inside, his father starts to realize how dangerous the 6 year old Gaara is becoming - who seemingly cannot control Shukaku the demon of sand, so decides to assassinate it. He sent several ninjas including Gaara's caring uncle Yashamaru who was teaching him to Love, but all was in vain. This all makes Gaara mentally unstable and therefore develops an extreme form of existentialism, killing anyone who taunts his existence.