Patrick Edward Purdy was born on November 10, 1964, in Tacoma, Washington. His parents were Patrick Benjamin Purdy and Kathleen Snyder. He had one older sister named Cynthia, born in August 1963. At the time of Patrick's birth, his father served in the U.S. Army and was stationed at Fort Lewis. After a dishonorable discharge, Patrick Sr. worked as a taxi driver.

When Patrick was two years old, his mother filed for divorce after a violent incident where his father threatened her with a gun. Following the divorce, Kathleen moved with her children to South Lake Tahoe, California, and later, they settled in Stockton. In Stockton, Patrick attended Cleveland Elementary School from kindergarten to second grade. Due to the divorce, he did not see his father much during his early childhood.

In October 1968, Kathleen remarried a man named Albert Gulart. They had one son together, Albert Jr. However, their home life was troubled. Kathleen often spent her time socializing and reportedly abused alcohol, sometimes in front of her children. Albert Gulart was known to physically assault Kathleen in the presence of his stepchildren. Patrick's stepfather later described him as quiet and emotional, with a reputation for being a loner among his peers.

In the fall of 1973, Kathleen and Albert separated. Kathleen moved her children from Stockton to Sacramento. In December of that year, Child Protective Services were called to investigate allegations of abuse and neglect. The children were taken into protective custody, but Kathleen eventually regained custody after agreeing to counseling.

In the summer of 1978, during a heated argument, Patrick struck his mother in the face. This led to him being banned from her house, which he felt was a significant abandonment. Patrick then lived on the streets of San Francisco for a time and briefly turned to prostitution before being placed in temporary foster care. Eventually, he went to live with his father in Lodi, California, who had moved there after his divorce from Kathleen.

Patrick enrolled in Tokay High School in September 1979, but he struggled academically and became an outcast. He attended school sporadically and began using drugs and alcohol. He accumulated a criminal record with charges including robbery and drug dealing. His father encouraged him to seek help, leading to limited results from a drug rehabilitation program.

On September 6, 1981, Patrick's father died in an accident, which caused further distress for him. After his father's death, Patrick faced homelessness and supported himself with odd jobs and petty theft before being placed with a foster mother in Los Angeles until he turned eighteen.

On January 17, 1989, Patrick Purdy carried out a shooting at Cleveland Elementary School in Stockton, California. He arrived at the school in his old Chevrolet station wagon. At around 11:40 a.m., he parked the vehicle and entered the playground carrying a semi-automatic rifle and two handguns. While about three hundred children were present, he began firing indiscriminately.

Purdy shot a total of 106 rounds during his attack, mainly targeting children. He took up a position behind a portable building and fired multiple rounds before changing locations to shoot other fleeing children. The attack lasted only about three minutes. In the chaos, he injured 31 people, including one teacher, and killed five children.

After the shooting, Purdy took his own life using one of the handguns he had brought with him. He shot himself in the head at about 11:48 a.m. Emergency responders found him still alive but he succumbed to his injuries shortly thereafter.

The victims of this attack were predominantly children of Southeast Asian ancestry, reflecting a significant population in the area. The aftermath of this event led to an outpouring of grief in the community and raised questions about gun control in the U.S.