|David Wang and George Chen were the joys of their parents' lives.
David, 20, kind and peaceful, was called a "math genius" with dreams of starting a computer business. George, 19, often donning his famous big smile, was a diligent student who, like David, was majoring in computer engineering at the University of California, Santa Barbara.
In an interview with CBS News, David and George's grieving parents spoke of the torment of losing their sons, the frustration of watching the media lavish attention on their sons' killer, and their aching desire for an end to the senseless violence plaguing their adopted country.
"We have love in our heart, tears in our eyes, responsibility on our shoulders, and we hear the voice from our children from heaven," said Kelly Wang, George's mother. "We want to do something."
"We are calling for the end of the killing of innocent people," said Jane Liu, David's mother, who said that as a hospital nurse, she faces death every day, but has found the loss of her son to be unbearable. "It's time for all Americans to wake up."
The parents of David and George are dismayed by the attention paid to their son's killer, whose manifesto and video rants recorded before the killings drew widespread coverage.
Focusing on Rodger, they said, creates the side effect of making him a celebrity, and may encourage other troubled kids to seek attention through violence.
"We want the young generation to know: Killing is a crime." said Kelly Wang. "Killing is not something cool."
The two families, immigrants from China who describe themselves as low profile and did not initially plan to speak out after the attack, said they instead want to focus attention on the victims and tell their story.
"In every photo of George, he's always smiling," said George's mother Kelly, as the two families sat around a table at the Wangs' Fremont home, with photos of the two young men spread out in front of them. "You never see a photo where he's worried or something. He always tried to put up his big smile everywhere."
In the photos, George is indeed beaming, whether posing with his dad, mom or -- smiling extra wide -- with his younger brother. "He loved to play with his little brother," Kelly Chen said.
"If you see those pictures, you can see how close we are," said Jane, of her son David. "Each time he would hold my shoulders, hold my hand. He was very very sweet."
"Their life was so short, so tragically taken," Johnny Chen, George's father, said of George and David. "They're like flowers even before the blossom."
The parents said they would have given their own lives in exchange for those of their sons, but they weren't given the chance. There's so much about the time leading up to the attack that they wish they could change. They wish the police had picked up on the killer's now apparent list of troubling signals. They wish the Rodgers family had done more to keep their son from committing his brutal crimes.
"We think good parenting is the first step to prevent the crime," said Kelly Wang. "Yes, you can do gun control, but if somebody has so much hatred in his heart, they can use other ways to kill innocents, and that happened to our boys."
Peter Rodger, the killer's father, will be the subject of an upcoming television interview, which has upset David and George's families. Rodger met with Richard Martinez, whose son was a victim. But when asked if they'd heard from the Rodger family personally, Johnny Chen, the father of George, said no.
"Personal condolence and apologize, and this is the minimum they should do," he said.
After CBS News reached out to Peter Rodger for comment late Wednesday, he sent the families a letter of apology.
Just a month after losing David and George, the two families are still coming to terms with the reality that they're gone.
"Rationally, we have accepted the fact," said Kelly Wang. "But in our heart, many times we still picture him coming back home."
"I still think my son is alive and not gone," David's father, Charlie Wang, said, with his wife Jane translating. "I still don't understand why this happened to such beautiful heart, beautiful lives."
For now, they can just remember the two decades they said they were blessed to have with their sons, young lives taken many decades too soon.