An artist helping to paint a street-side anti-violence mural in Oakland was shot and killed on Tuesday, authorities said.

Oakland police spokeswoman Johnna Watson said Wednesday officers were searching for the shooter as friends mourned Antonio Ramos, 27, during a vigil at the mural site. Watson said an argument led to the shooting at the site under an Interstate 580 overpass in West Oakland.

Ramos was one of 10 artists who were working on a project to help spread peace and stop violence. He reportedly quarreled with a man who wasn’t part of the group. The incident escalated, and the man shot Ramos and ran away, police said. No one else was injured.

Watson declined to give further details about the crime while the investigation is ongoing.

The idyllic painting of trees, a creek and brightly colored Victorian houses contrasts sharply with parts of West Oakland that are struggling to cope with drugs, poverty and violence.

Oakland has had 73 homicides this year, and many have happened on the western end of the city.

Officials say there is nothing to indicate the subject matter in the mural, called the Oakland Super Heroes Mural Project, sparked the violence.

"I think this is an isolated incident," said Aeeshah Clottey, one of the founders of Attitudinal Healing Connection of Oakland, a group that seeks to stop violence by inspiring people with art and education. The 25-year-old organization was sponsoring the mural project.

Ramos started volunteering with the group in 2012 after being inspired by its work on a student-designed mural.

"He kept walking past it every day, and he finally asked if he could help out," Clottey said.

Ramos worked on that painting on San Pablo Avenue and was just starting to paint the current project.

"He was a very nice person," Clottey said. She referred further questions to his mother, who was not immediately available for comment Wednesday.

Clottey said the shooting is emblematic of a larger issue of violence around the world.

"This is indicative of a global problem," she said. "And we want to look at ways to inspire peace."

The Oakland Super Heroes Mural Project told the Los Angeles Times Tuesday Ramos’ death was a result of “senseless gun violence that continues to plague our communities.”

The group plans on continuing to work on the mural as a way to commemorate Ramos.

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The Associated Press contributed to this report.