A bank robbery was thwarted Friday morning by an armed security guard, according to Medford police.

A robbery was reported at 9:52 a.m., at Chase Bank, 81 E. Stewart Ave., in Medford. The suspect was detained by on-site armed security, police said.

The suspect, Brian Ernest Ramos, 32, was not armed, police said.

Ramos was arrested for second-degree robbery and a misdemeanor count of second-degree disorderly conduct. He was being held without bail in the Jackson County Jail.

Police said Ramos was on probation for robbery.