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A 31-year-old Los Angeles police officer who has been with the department for a decade has been arrested after allegedly having a sexual relationship with a 15-year-old cadet who was herself arrested in connection with the theft of police vehicles, Chief Charlie Beck announced Thursday in the latest installment of a continuing scandal involving the cadet program.

Robert Cain in seen in a photo displayed at an LAPD news conference on June 22, 2017. (Credit: KTLA)

Officer Robert Cain was arrested at 11 a.m. Thursday on suspicion of unlawful sex with a minor, also known as statutory rape. For the past two years, Cain has been assigned to be the equipment room operator at 77th Street Division, Beck said.

The chief went to the division to arrest Cain himself, cuffing the suspect.

“I find the actions of Cain, if they are proven, to be despicable. I find them to be absolutely inconsistent with the ethics and standards of the Los Angeles Police Department, and they are criminal, and I’m a police officer,” Beck said in announcing the arrest.

The development comes just two days after Beck disclosed that a total of seven cadets have been arrested in connection with the theft of several LAPD patrol vehicles.

The teen allegedly involved with Cain – in what Beck said was a “short-term relationship” over the last month – was one of four cadets arrested more recently. She was assigned to 77th Street Division.

Three initial cadets were arrested after the embarrassing scandal unfolded last week, when police officers gave chase to two patrol vehicles that had been discovered missing on June 14. The patrol vehicles, driven in tandem, split up, with officers in pursuit.

Both vehicles crashed in two separate locations in the South L.A. area, and the two drivers and a passenger – all cadets – were taken into custody. They had taken three police vehicles; the third vehicle was found near 77th Street Division after the cadets were questioned.

The cadets were familiar with LAPD’s vehicle tracking systems and were able to sign the black-and-whites out of an automated vehicle inventory system, logging in as a vacationing sergeant, Beck said last week.

On Thursday, the chief said that Cain “had knowledge of and has been involved in the unlawful use of police equipment, including cars, by 77th and other cadets,” Beck said.

It’s possible Cain’s alleged relationship with the teen was connected to her access to police equipment and cars, Beck said.

“That would be consistent with pedophile-type behavior,” the chief said.

After the pursuits and arrest of the initial three cadets, investigators recovered two LAPD Tasers, two police radios and an expired bullet-resistant training vest, which was being worn by one cadet, the chief has said. No police firearms were missing.

Now detectives are getting search warrants for Cain’s home, vehicle, locker, phone and other social media.

LAPD detectives could be seen moving a cache of weapons from Cain’s Rancho Cucamonga home on Thursday evening, including what appeared to be numerous rifles. Neighbor Myrna Wong said she usually sees Cain every day, calling him “very helpful.”

Investigators became aware of Cain as a suspect on Wednesday, Beck said, after a search of the alleged victim’s phone led to text messages that were thought to “indicate inappropriate behavior.” Cain was then placed on surveillance.

Cain has no “significant” history of discipline or use of force, and was not involved with any LAPD youth programs, Beck said.

At this point in the investigation, there’s no indication other sworn LAPD personnel were involved, the chief said, indicating that could change.

Investigators are trying to determine if the equipment taken by the cadets was used for any criminal or gang activity. Beck indicated earlier this week that the cadets may have illegally conducted one or two traffic stops.

The department’s best detectives are on the case, Beck said, including those who investigated the “Grim Sleeper” serial murder case that led to the conviction of Lonnie Franklin Jr. last year.

The only adult among the arrested cadets has been identified as 18-year-old Leonel Roberto Flores, who was held on suspicion of unlawful driving of an emergency vehicle. A cadet named Roberto Flores was South Bureau’s cadet of the year in 2015, according to the LAPD Cadet blog.

Beck ordered a complete review of the 2,300-member cadet program, as well as LAPD systems for tracking equipment and vehicles. The cadet programs at 77th Street Division, where six of the cadets worked, and Pacific Division, where one worked, have been suspended.

The Los Angeles Police Protective League, the officers’ union, has faulted staffing levels in the department in offering sharp criticism over the cadet incidents.

“This is unforgivable and it’s a black eye to the LAPD,” said T.J. Tarjamo, director of the union, earlier this week.

On Thursday, the union issued a statement applauding the arrest of Cain.

“There should be zero tolerance for any officer who takes advantage of those they are entrusted to protect. We are deeply disturbed by this development and condemn this officer’s alleged actions in the strongest possible terms,” the union said.

Beck said he plans to require all cadets to attend Saturday’s graduation ceremony for new LAPD officer recruits. He intends to send a message of support for the program and the rest of the cadets.