Archbishop Salvatore Cordileone joined other members of the archdiocese who regularly hold vigils for murder victims in San Francisco.
The latest victim was Cameron Myers, who was killed early last Wednesday near Innes Avenue and Aurelius Walker Drive, police said.
Cordileone and about a dozen others prayed and sang for Myers and his family.
"These moments of sadness, of mourning and of outrage are times when we just need to be together in solidarity," Cordileone said.
He said the religious community can help young people resolve conflicts and "develop a sense of self-worth and virtue."
The Rev. Paul Gawlowski from the Bayview District-based St. Paul of the Shipwreck church said, "So many of our youth are lost due to hopelessness and violence."
Gawlowski said the neighborhood also loses "so much potential on the other end by people that overcome obstacles but then have to leave the community" because of a lack of jobs.
Angela Alioto, former president of the San Francisco Board of Supervisors, was also at the vigil, and said jobs are indeed the key to preventing violence.
"You've got to give them jobs so they're not on the streets and so they feel good about themselves," Alioto said.
She noted that the fight to improve the Bayview-Hunters Point neighborhood dates back to her tenure on the board in the 1980s and 1990s -- and even beyond that, to the time when her father, Joseph Alioto, was mayor from 1968 to 1976.
"I'm sorry we're still here, but the fight's not over," she said.
A 15-year-old boy was arrested on Sunday in Nevada County for Myers' murder and is awaiting extradition back to San Francisco, police spokesman Officer Albie Esparza said.