Officer Robert Cain, 31, allegedly had sex in the past month with a teenager suspected with other cadets of being involved in the recent thefts of police cruisers and other LAPD equipment, Beck said. Cain also allegedly knew of, and helped facilitate, the string of thefts that has rattled the department in recent days, Beck said.
"There may be a connection between the wooing of this underage female and access to the equipment. I don't know," the chief added at a news conference. "I know that would be consistent with pedophile type behavior."
Beck said he personally arrested Cain at the department's 77th Street Division station around 11 a.m. on Thursday.
"I find the actions of Cain, if they are proven, to be despicable and I find his actions absolutely inconsistent with the ethics and standards of the Los Angeles Police Department," he said.
Cain's bail was set at $75,000.
The latest allegations swirling around the troubled cadet program drew condemnation from city leaders, with one city official calling for an audit of all of the department's youth programs.
Investigators learned of the sexual misconduct allegations on Wednesday, as part of a larger review of the theft of three LAPD cruisers and other equipment. Detectives uncovered text messages between Cain and the victim that detailed "inappropriate behavior," and showed the officer knew about the alleged thefts, according to Beck.
Cain was placed under 24-hour surveillance as soon as his name surfaced in the investigation, Beck said.
Cain was the officer assigned to the equipment room at 77th Street Division, according to Beck, who earlier this week said lax security of the station's equipment locker may have played a role in the alleged theft of squad cars, bulletproof vests, police radios and Tasers by LAPD cadets.
Beck described the relationship between Cain and the cadet as "short-term," and said none of the sexual encounters took place on LAPD property. Cain was not assigned to the department's youth programs and does not have a significant disciplinary history, Beck said.
Detectives began searching Cain's locker, residence and social media accounts on Thursday for evidence of any other sexual misconduct. At this time, police do not believe any other sworn personnel were involved, Beck said.
The case has not yet been presented to the Los Angeles district attorney's office, according to a spokeswoman for the agency. It was not immediately clear if Cain had an attorney.
Investigation of the sexual misconduct allegations grew from an ongoing review of the LAPD's cadet program. Last week, Beck said three cadets had been arrested and accused of stealing three cruisers from department garages. Officers chased two of the stolen cruisers through South L.A. on June 14, resulting in separate car crashes.
The search for the stolen cruisers quickly focused on a 16-year-old female cadet, Beck said last week. Two other teenage cadets, boys aged 15 and 17, were also arrested.
Four more cadets, aged 14 to 18, were arrested as the inquiry unfolded, police said earlier this week.
The only adult cadet arrested in the probe was identified as Leonel Flores, an 18-year-old from Los Angeles. The others have not been identified because they are minors.
Six of the cadets were assigned to the 77th Street Division. Beck has suspended the cadet programs at the 77th Street and Pacific divisions pending further review.
Cain's alleged actions were quickly denounced by city leaders.
“There is no higher priority than protecting and guiding our young people — and when they become LAPD cadets, every parent should feel confident that they will be treated with the utmost care every step of the way. The charges against this officer are deeply disturbing, and I have been assured he will be prosecuted to the fullest extent of the law,” Mayor
Beck last week announced a "top-to-bottom" review of the LAPD's cadet program, but Englander's motion would expand the review to other youth programs including the Gang Reduction and Youth Development and Police Activities League Supporters programs, according to Colin Sweeney, the councilman's communications director.
The motion would also require that findings of the investigation be made public.
The Los Angeles Police Protective League, which represents rank-and-file police officers, also harshly criticized Cain on Thursday.
"If these disgusting allegations are true, we applaud the department for taking swift action to arrest this individual for this vile crime," the union said in a statement. "There should be zero tolerance for any officer who takes advantage of those they are entrusted to protect."
Matt Johnson, president of the Los Angeles Police Commission, a civilian panel that oversees the department, said: "Chief Beck has been very clear that there will be a complete investigation into these allegations — which in no way reflect the courage and integrity that define the 10,000 members of the LAPD and the 2,000 Cadets who work hard every day to better themselves and serve their communities."
LAPD brass has long pointed to the cadet program as a success story. Thousands of young people, 13 to 20 years old, have participated over the years. The goal is to foster relationships between the city's youth and police while helping participants develop skills that will aid them later in life.
Beck is scheduled to speak to the entire cadet class at a graduation ceremony Saturday, and has repeatedly said he hopes the continually unfolding scandal does not tarnish the program as a whole.
"I intend to go forward Saturday with the graduation," the chief said. "I hope the media attend so they can see the other 2,200 cadets who so well serve this city."
7:50 p.m.: This article was updated with additional comments from Mayor Eric Garcetti, the Los Angeles Police Protective League, City Councilman Mitchell Englander and Police Commission President Matt Johnson.
4:30 p.m.: This article was updated with additional details from Beck.
4:15 p.m.: This article was updated with details about the investigation from LAPD Chief Charlie Beck at a news conference.
3:35 p.m.: This article was updated with details of the officer's arrest.