Sheriff’s detectives arrested a known sex offender in downtown San Luis Obispo on Wednesday afternoon as he logged on to Facebook at the Apple Store on Higuera Street.

Robert Nicholas McGuire, 35, is being held without bail at the San Luis Obispo County Jail on suspicion of violating his probation.

The detectives, including members of the Sexual Assault Felony Enforcement team, spotted McGuire downtown. One of them recognized McGuire from a previous child pornography case, according to a Sheriff’s Department news release.

McGuire began to log on to the Internet from a display computer, the Sheriff’s Department wrote. At the same time, a detective went to the computer next to McGuire and logged on to the Megan’s Law website.

He retrieved information “that clearly indicated McGuire was prohibited from using the Internet,” the department said.

Officers took McGuire into custody after he left the store.