That woman eventually takes the can of black paint from them.
The relationship between the two people who were seen defacing the mural was unknown, and it was unclear what charges they could face. Police officials were not immediately available to comment on Sunday night.
Justin Gomez, a local resident who got permission from the city to paint the mural, said of the vandalism on Sunday: “I’m not so surprised that it happened. I’m surprised at how bold they chose to be.”
The mural was painted on a one-block stretch of Court Street in Martinez, which is about 35 miles northeast of San Francisco. The city selected the location after Mr. Gomez, the lead organizer for Martizians for Black Lives, asked the city for permission to paint the message, he said.
“We asked to do it on our city’s main street,” Mr. Gomez said. The city, he said, offered the street in front of the Wakefield Taylor Courthouse instead.
“We immediately agreed to it,” he said, “and I feel it was a more powerful statement than what we had initially proposed.”
Mr. Gomez and local residents started painting the mural at 7 a.m. on Saturday; by 2:30 p.m., with the paint still drying, he left.
By 3 p.m., Mr. Gomez said, he received messages saying the mural was being vandalized.
Mr. Gomez said that the mural had since been restored and that supporters were “maintaining a presence” to prevent further damage.