Larry Brinkin, 66, had previously been arrested in June on similar charges, but prosecutors declined to file charges and requested that police investigate the case further, police spokesman Sgt. Mike Andraychak said.
Police eventually developed enough information to obtain a $240,000 arrest warrant for Brinkin, who turned himself in at the Hall of Justice at about 10:30 a.m. today, Andraychak said.
He was booked into county jail on suspicion of two felony counts of possession and distribution of child pornography, and could make his initial court appearance as soon as Friday, according to Andraychak.
Brinkin worked for 22 years with the Human Rights Commission before retiring in 2010.
The Board of Supervisors passed a resolution that year proclaiming Feb. 1-7, 2010, "Larry Brinkin Week" in San Francisco because of Brinkin's advocacy work for LGBT issues.