New York City Mayor Bill de Blasio urged the city's pension funds on Friday to divest their holdings in stocks of gun makers after this week's mass shooting in San Bernardino, California.

Two of the funds in the city's $155 billion pension system ditched their holdings in gun manufacturers such as Smith & Wesson Holding Corp and Sturm Ruger & Co Inc after the Sandy Hook school shooting in 2012.

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Those two funds were the New York City Employees Retirement System and the New York City Teachers Retirement System. Funds for the city's police and fire departments as well as the city's board of education have not divested their holdings.

"I call on all government pension funds in New York City and across the country to divest immediately from funds that include assault weapon manufacturers," de Blasio said in a statement.

The comptroller's office, which oversees the pension funds, did not immediately comment. It was not immediately clear which gun stocks, if any, are held by the other three funds.

"I am urging the city comptroller to divest as soon as possible if no verifiable assurance is given that assault weapons will not be sold to civilians," the mayor said.