Garcia, 20, was one of five young people slain last week at Northern Illinois University by a gunman whose girlfriend said he recently stopped taking his antidepressants.
At a memorial service for Garcia on Sunday, hundreds of friends, family and well wishers filled a suburban Chicago funeral home to pay their respects. One young woman wore a homemade, pink and white T-shirt that read, "R.I.P. Cathy."
"It's like the all-American dream cut short," said her brother, Jaime Garcia.
Her funeral was set for Monday.
The tragedy hung over Sunday church services throughout the region, from the university's home in DeKalb on Chicago's western exurban edge, to Elk Grove Village, where the gunman grew up, to blue-collar Cicero bordering Chicago.
Investigators still haven't determined what set off 27-year-old shooter Steven Kazmierczak, who opened fire during a science lecture with a shotgun and pistols, then committed suicide.
Kazmierczak grew up northwest of Chicago, in Elk Grove Village, and played saxophone in the school band. He spent time in a mental health center in his late teens, and police have said without elaboration that he had stopped taking some kind of medication in the days or weeks before the shooting.
His girlfriend, Jessica Baty, told CNN on Sunday that he had stopped taking an antidepressant about three weeks ago because "it made him feel like a zombie."
She said he called her early on Valentine's Day, the day of the shooting, to say goodbye. "He told me not to forget about him," she told CNN.
The day of the shooting or the day after, Baty received a package from Kazmierczak containing two textbooks, a cell phone and what she characterized as a "goodbye note."
"You've done so much for me," the note said, according to Baty. "You will make an excellent psychologist and social worker someday." Another package contained a gun holster and ammunition.
Baty described an on-off relationship to CNN and said she and Kazmierczak most recently had been living together. "I still love him," she told CNN.
Residents of Elk Grove Village seemed to feel a sense of disbelief and confusion over the attack that thrust their community into the news, said the Rev. Hwa Young Chong at the Prince of Peace United Methodist Church.
"I couldn't believe coming from a place like Elk Grove he could do that," said Judy Glomski. "It's just a friendly town. I guess there are sick people everywhere."
Kazmierczak was studying sociology at NIU. He transferred three semesters ago to the more prestigious University of Illinois in Champaign. Most students and professors on both campuses remembered him as a promising student.
Yet he began assembling an arsenal in August, buying a shotgun and three menacing handguns from a small Champaign gun shop. He added oversized ammunition clips in an Internet purchase from the same dealer that sold the Virginia Tech gunman a weapon.
Kazmierczak had also begun the long process of having his arms blanketed with disturbing tattoos, including a skull pierced by a knife, a pentagram and a macabre character from the "Saw" horror movies, superimposed on images of bleeding slashes across his forearm.
In addition to Garcia, the dead were Daniel Parmenter, 20, of Westchester, Ill., Ryanne Mace, 19, of Carpentersville, Ill., Julianna Gehant, 32, of Mendota, Ill., and Gayle Dubowski, 20, last of Carol Stream, Ill.
Parmenter, whose funeral is set for Tuesday, stood taller than 6 feet and played rugby and football. He also was quiet, studious and introspective, recalled Joe Morgan, who served as his confirmation mentor.
"He was a big kid who was gentle," Morgan said.
At First Baptist Church in DeKalb, members passed pinned-on red ribbons for a morning service Sunday. The Rev. Joe Sanders prayed for the NIU community and the victims' families and asked God to help Kazmierczak's family cope with the attack and their own grief of losing a son: "We want God to be merciful and gracious to them."