Police were called to a residence on the 200 block of North Vine Avenue at about 9:49 a.m. Wednesday.
A 41-year-old woman told responding officers had entered her home through an unlocked door and sexually assaulted her. The woman told police the man was armed with a handgun. He left before police arrived.
Officers located the suspect walking in the area on the 500 block of West Holt Boulevard and arrested him. He was carrying a realistic-looking pellet gun.
Police were investigating a similar incident that occurred about an hour earlier nearby on the 100 block of North Pleasant Avenue. A suspect unsuccessfully attempted to break into a residence there.
Ontario resident Daniel Anthony Aguirre, 20, was arrested on charges of burglary and assault.
Anyone with information about the case or similar incidents is encouraged to contact Ontario Police at (909) 395-2001.