According to the Los Angeles County Sheriff's Department, deputies responded to a medical emergency call on the 1500 block of Janlu Avenue just before 1 p.m. Saturday.
Bishop David O'Connell was found in the room of a home with a gunshot wound to the upper torso. The 69-year-old, who was a priest and later a bishop in L.A. for 45 years, was pronounced dead at the scene.
The sheriff's department, which initially described the incident as a suspicious death, has not released information regarding a suspect or suspects. Investigators told ABC News that suicide was ruled out overnight.
No further details were available.
LA bishop shot and killed in Hacienda Heights, authorities say
Shortly following the announcement from authorities, Archbishop José H. Gomez released the following statement:
"We learned early this morning from the Los Angeles County Sheriff's office that they have determined that the death of Auxiliary Bishop David O'Connell yesterday was a homicide. We are deeply disturbed and saddened by this news.
Let us continue to pray for Bishop Dave and his family. And let us pray for law enforcement officials as they continue their investigation into this terrible crime."
O'Connell's death prompted words of grief and solace from city officials and other notable figures, including former L.A. Mayor Eric Garcetti.
Devastated parishioners gathered by the crime scene Saturday as deputies investigated.
"It broke me and I was scared to tell my wife because my wife loved him so much," said parishioner Johnny Flores.
Glendy Perez, another parishioner, said O'Connell "was an humble soul."
"He was not the type that would have confrontations with nobody," she said. "He was very loving, and he had like a gift of healing. When you would attend his ceremonies, it was like a gift of healing."
O'Connell, who was born in Ireland in 1953, was named an auxiliary bishop for the Archdiocese of Los Angeles by Pope Francis in 2015.
He studied for the priesthood at All Hallows College in Dublin and was ordained to serve in the Archdiocese of Los Angeles in 1979. After ordination, he served as associate pastor in several parishes and as pastor at several parishes in L.A.
He was the chairman of the Interdiocesan Southern California Immigration Task Force, helping coordinate the church's response to immigrant children and families from Central America.
Meanwhile, anyone with information about the death is urged to call homicide detectives at 323-890-5500 or Crime Stoppers at 800-222-8477.