A lawyer says one of four San Francisco police officers under department investigation over racist and homophobic texts has resigned.

The San Francisco Chronicle reported (http://bit.ly/1C1n5WX) Thursday that attorney Anthony Brass said his client, 46-year-old Michael Robison, resigned on Wednesday.

Robison had been transferred from the special victims unit to the horse-mounted unit as the department investigated the sending of texts in 2011 and 2012 targeting blacks, Mexicans, Filipinos and gays.

The newspaper said Robison, who has been openly gay since before his hiring in 1992, came under intense pressure after word of the texts became public.

Police Officers Association President Martin Halloran has told the newspaper that at least 10 additional officers are under investigation.