Laguna Beach Police say the suspect is a 46-year-old homeless man. He's facing a charge of lewd conduct.
Laguna Beach Police allege Joseph Cormier was sitting at a computer at the Laguna Beach Library watching pornography and engaging in a lewd act.
Another man noticed what he was doing and reported it to police.
"We meet with the man that was at the computer touching himself," said Laguna Beach Police Lt. Jason Kravetz. "He had already finished looking at the images on the computer, and he was up near the front door, and our victim here placed him under private-person's arrest for lewd conduct."
Friends of the Library group president Martha Lydick wants to see changes at the library, such as setting up an area where views of the computer screens are blocked from others.
"All of my friends are upset right now because they don't want to see it, period," said Lydick. "They're not interested in pornography. They want to be porn-free."
"We do have filtered access for children and teens, but we do have unfiltered computer access throughout our county libraries," said Jenny Gasset, branch manager of the Laguna Beach Library. "We don't monitor what people are viewing. It's their First Amendment right and their legal right to do the research that they need to do, to access the things that they need to access."
Police say it is not illegal to look at porn, but it becomes criminal if children are around at the time.
Police say no children were present during the act.