Redlands resident Nathan Gastineau, 30, was arrested at 9 p.m. after numerous interviews with investigators acting on information they received earlier.
Gastineau, a 10-year veteran of the department assigned to the Highland station, was booked into West Valley Detention Center on one felony count of lewd acts with a child. He was released on $25,000 bail.
The victim's father said Gastineau was the leader of the Explorers group at the Highland station, which is where he met the girl. He also said his daughter was part of an Inland Empire "Ghost Busters" fan group that Gastineau co-founded.
"He's a sheriff's deputy of San Bernardino County, he's sworn to uphold the law and be honest and have integrity," the victim's father said. "This was just a way for him to get my daughter into bed."
Gastineau was placed on administrative leave pending the outcome of the investigation.
He is scheduled to be arraigned sometime next week.
No other information was released to protect the minor.