But what led to the attack? What sparked the rage of two brothers raised in a seemingly comfortable, middle class, suburban Snellville household? How did things get so bad?
Testimony during Monday's hearing did not shine much light on what straw, specifically, broke the camel's back, or if there even was one. But it better showed how years of simmering familial tension, drug and alcohol abuse and possible mental health battles finally came to a boil.
After Christopher Ervin graduated from Shiloh High School, he went to the University of Charleston in West Virginia to play football. His dad had played in college — was a "star," according to a Gwinnett County police detective — and he had big shoes to fill.
Christopher's time in West Virginia, though, was short lived. He left after only a year, and transferred to Valdosta State University. He soon, however, didn't have enough money to continue or enough credits to graduate.
He moved back home, eventually tried finishing at Georgia State, and failed.
Air Force? Failed drug test. Job working a forklift at his father's company? Failed drug test.
He got into a car accident where, according to his father, Zachary, he'd been drinking but let off by the responding police officer. His father later found Xanax in the pocket of the pants he'd been wearing.
His parents knew he'd been smoking pot, they said Monday, but didn't realize the extent of his problems.
"Before I came here, before I was arrested, I honestly was at the lowest point in my life," Christopher Ervin said during the hearing. "After graduating high school, I increased drug use to the point where it became not only something that I felt that I needed to have, to cope through my days, but it was also something that hindered me from being my best."
While his older brother struggled, Cameron Ervin was doing much of the same. He played in the marching band and was a smart kid, but he also battled a bad temper, had "issues not coming home" and had girls over when he wasn't supposed to.
He too fell into drugs, often ones shared by Christopher.
Zachary Ervin began to notice money being taken from his dresser. He made his sons take lie detector tests, and Cameron's "showed deception."
Both brothers were "resentful" of the test, the father told police.
"I spent so much time in my life holding a grudge and hate in my heart against my family, my parents especially, for thing that they did in the past, even though it was for the best and I didn't realize it," Cameron said on Monday, his 19th birthday. "And I tried to combat that with drug and alcohol abuse."
During one of their regular jailhouse visits, he would tell his parents that the days and weeks and months before the attack were filled with "bouts of just not feeling adequate, not measuring up."
"He stated that, during the incident, it was like a, he used the term of a 'black silhouette,' over him," his mother, Yvonne, testified Monday.
A psychological exam administered after Cameron's arrest suggested he could have narcissistic personality disorder, and theory that was also arrived at after he, as a younger teenager, went to a doctor to be tested for ADHD.
Cameron's parents recently launched a nonprofit foundation which appears to be especially inspired by his struggles.
"Fighting For Forgiveness, Inc. was founded as a result of a traumatic family event in September of 2015," its website says. "It gave us personal insight into the world of depression and how detrimental it can be when it goes undetected.'
'Something seriously wrong'
A dozen people testified on behalf of Christopher and Cameron Ervin before they were sentenced Monday. Ten of them said the brothers were good kids from a good family, and that they had no idea what could've led to last September's events.
The other two — Yvonne and Zachary Ervin — also vouched for their sons.
"There's nothing that I know of ... that could cause such an act other than the fact that there was something, it had to be something seriously wrong," the father said.
"These are not the sons we raised," the mother said. "My sons would not do something like this."
While the brothers weren't drug tested after their arrest and, at least publicly, have never explicitly said they were drunk or high at the time of the attack, Yvonne Ervin hasn't been shy about theorizing as much.
In a letter sent to Judge Ronnie Batchelor in January, she suggested they were "given some type of hallucinogen, like PCP, without their knowledge."
Whether she was grasping at straws, correct in her assessment or somewhere in between, she can't be blamed for trying to parse out an explanation -- just like everyone else.
"I just tried to kill my [expletive] parents," Cameron Ervin told a police officer shortly after his arrest. "Who does that?"