SAN JOSE (CBS SF) — A 70-year-old San Jose man has been arrested on kidnapping and sexual assault charges involving a 13-year-old girl, whose parents had hired him to pick her and her friends up at school, police said.

San Jose police said Tuan Binh Nguyen was booked into Santa Clara County Jail Monday on charges of false imprisonment and committing lewd acts with a child.

According to investigators, officers responded to a call from a private armed security guard at Capitol Expressway and Tuers Road at about 3:35 p.m. on Monday. The guard told police he had interrupted a suspect sexually assaulting a juvenile female and was holding him at gunpoint.

The preliminary investigation revealed the victim’s family had hired Nguyen several years ago to drive the victim home from school. On January 13th, he allegedly dropped off the other children, leaving the victim alone in his vehicle.

Nguyen allegedly deviated from the route to the victim’s home, parking behind a business in the 1000 block of E. Capitol Expressway.

The security guard approached the suspect’s vehicle and observed him sexually assaulting the young girl, who was attempting to fight off the attack. The security guard then took the suspect into custody at gunpoint and turned him over to arriving officers.

Anyone with information about this case or similar incidents involving this suspect is asked to contact Detective Ed Sandoval or Detective John Tran of the San Jose Police Department’s Sexual Assault Investigations Unit at 408-277-4102.

Persons wishing to remain anonymous may either call the Crime Stoppers Tip Line, (408) 947-STOP (7867), or click the “Submit a Tip” link below. Persons providing information leading to the arrest and conviction of the suspect may be eligible for a cash reward from the Silicon Valley Crime Stoppers.