Story highlights Police say memorial was vandalized with red paint

"Justice for Alton" scrawled in front of statue

Police Chief says his officers are "on edge" after Dallas attack

(CNN) A memorial honoring fallen police officers in Richmond, Virginia was vandalized with red paint, authorities said.

The Richmond Police Memorial statue was vandalized early Wednesday morning, according to authorities. Someone had painted the statue's face red and marked a red 'X' on its chest.

The words "Justice for Alton" were scrawled on the paving stones in front of the statue -- apparently in reference to Alton Sterling . Sterling was killed by police in Louisiana last week. His death helped spur nationwide protests against excessive force by police.

"This is a cowardly act for someone to come and air his or her grievances at a memorial in honor of 28 police officers," said Richmond Police Chief Alfred Dunham.

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