"I thought it would be the very best thing for us to move forward and have a reorganization and have a new mayor," former Mayor Dennis Kneier told local reporters.
In an official statement, Kneier said he wished to end public humiliation for himself and San Marino for the June 7 incident.
"As is well known, early in the evening of Saturday, June 7, I had a lapse of judgment and discarded dog waste on a neighbor's walkway," Kneier said.
"It was insensitive, disrespectful and wrong. I have apologized to my neighbor for my action, and I will pay a fine for littering. I can understand why this matter has some questioning my ability to lead the council. I want to assure you that something like this will not happen again."
According to Kneier's neighbor Philip Lao, the mayor threw the excrement due to a 6-year-old feud over Lao's opinion of Kneier's politics. Kneier will remain on the San Marino city council until his term ends in November.