The service for Christina Anderson, 44, and Ethan Anderson, 8, was held at the Guardian Angels Roman Catholic Church in Santee.
"For the death of Tina and Ethan there are no easy words," the Rev. Kevin Casey told the memorial gathering. "We struggle with deaths like this because they are not right. They are an abomination."
The two were killed, allegedly by family friend James DiMaggio, in DiMaggio's home in Boulevard in rural San Diego County on Aug. 4 before he kidnapped Hannah and fled north. Sheriff's investigators say DiMaggio set fire to the home before leaving town.
Mother and son died from "horrific and cruel murders," Casey said. "We are touched by this evil and we can never be the same again."
After an Amber Alert and six days of a massive search, DiMaggio and Hannah were spotted in the rugged Frank Church River of No Return Wilderness in Idaho. On Aug. 10, DiMaggio was shot and killed by FBI agents sent to rescue the teenager.
San Diego County Sheriff Bill Gore said later that Hannah did not know that DiMaggio had killed her mother and brother. The teen was being held under "great duress," Gore said.
The fire that destroyed DiMaggio's home was set with incendiary devices, probably with timers, investigators said.
Back in her home in Lakeside, Hannah took to social media to answer questions about the ordeal.
"I'm a teenager," she said during an interview on NBC's "Today" show. "I'm gonna go on it."