There are still many questions unanswered about how Holmes, now 24, went from the quiet teen in California to an alleged mass killer in Aurora, Colo. But just hours after the massacre, a clearer portrait was emerging of his life leading up to it.
Holmes graduated from Westview High School in San Diego in 2006, a school district spokeswoman, Tina McDowell, told TPM. His neighbors described him as a shy, Presbyterian churchgoing teen.
"I saw him as a normal guy, an everyday guy, doing everyday things," neighbor Anthony Mai, 16, told the Los Angeles Times.
Reporters flooded his former neighborhood after the killing, lining up in front of the house where his parents still live. Police were called to keep reporters at bay.
San Diego police spokeswoman Lt. Andra Brown said the family was deeply upset and just wanted privacy. She said the suspect's father was escorted from the house early in the morning but declined to say where he was headed. She also released a statement from the family.
"Our hearts go out to those who were involved in this tragedy and to the families and friends of those involved," the unsigned statement said. "We ask that the media respect our privacy during this difficult time. Our family is cooperating with authorities in both San Diego, California and Aurora, Colorado. We are still trying to process this information and we appreciate that people will respect our privacy."
After high school, Holmes enrolled in the neuroscience program at the University of California, Riverside. Chancellor Timothy White said at an afternoon news conference that Holmes was an honor student who earned merit scholarships and graduated in 2010.
"Academically, he was at the top of the top," White said. "He distinguished himself from an academic point of view during his four years with us, graduating with the highest honors."
For graduate school, Holmes moved out of state and enrolled in a neurosciences graduate program at the University of Colorado Denver. Dan Meyers, a spokesman for the school of medicine, confirmed to TPM that Holmes had been a student on campus there.
But something changed in recent weeks. The Denver Post reported that Holmes was in the process of withdrawing from the school. A neighbor in Aurora, Colo., told the Huffington Post that Holmes appeared stone cold, carrying two black bags into their apartment building a day before the killing.
Then on Friday, authorities said Holmes drove his white Hyundai sedan to the nearby Century 16 movie theater that was screening midnight showings of the premier of the Batman movie, "The Dark Knight Rises."
Holmes was dressed all in black and wearing a helmet, a bullet-proof vest, armored leggings, a groin protector and a gas mask when he walked into the theater. Aurora Police Chief Dan Oates said the young man brought an assault rifle, a shot gun and at least one .40 caliber Glock pistol with him.
Holmes allegedly then opened fire on the sold-out theater just a short time after the movie began. Authorities said the 911 calls started to come in at 12:39 a.m. In the end, 71 people had been shot. The police chief said officers found Holmes in the parking lot behind the building. As of Friday afternoon, 10 bodies were still in the theater.
There was no credible information early after the massacre about what motivated the gunman. He was in custody, but it was unclear whether he was cooperating with authorities. Denver television KUSA reported that he was expected to make his first court appearance on Monday.
Meanwhile, Oates said bomb technicians were dealing with what appeared to be "sophisticated" booby traps rigged in Holmes' apartment. Five buildings in the area had to be evacuated.
Almost every major political leader in the U.S., including President Obama, offered their condolences by the end of the day. Colorado Gov. John Hickenlooper, however, offered a cold assessment of the gunman that had torn apart his state.
"This is the act apparently of a very deranged mind," Hickenlooper said. "We will come back stronger than ever, although obviously it will be a very, a very hard process."
Eric Lach and Igor Bobic contributed to this report.