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A 31-year-old Los Angeles Police Department Officer was booked on felony weapons charges amid an ongoing criminal investigation into the officer allegedly having sex with a 15-year-old female cadet, according to the LAPD.

Robert Cain is facing 10 felony weapons charges after he surrendered himself to the San Bernardino County Sheriff’s Department in Rancho Cucamonga Thursday. LAPD  investigators found more than 100 firearms —- including assault rifles and several weapons determined to be illegal in the state of California — at Cain’s Rancho Cucamonga home back in June, police said.

On Friday, Cain pled not guilty to all counts and his bail was set at $250,000, according to the San Bernardino District Attorney’s Office.

Cain first came to the attention of authorities after they uncovered texts between him and a 15-year-old cadet that seemed to be indicative of an inappropriate sexual relationship between the two, police said. The discovery was made while LAPD officers were investigating the theft of two patrol cars by cadets in the department.  Cain is currently facing felony charges for unlawful sex with a minor.

On Wednesday, the San Bernardino County District Attorney’s Office charged Cain with 10 felony weapons crimes — including the illegal possession and manufacturing of assault rifles — after receiving evidence from the LAPD investigators who searched Cain’s home, police said.

Cain surrendered himself on Thursday and was taken into custody of the San Bernardino County Sheriff’s Department in Rancho Cucamonga.