Ten local police officers in Northern California were arrested and charged on Thursday after a series of F.B.I. raids stemming from a two-year investigation that the authorities said had uncovered a raft of crimes, including falsifying records to receive raises, illegally distributing drugs and improperly deploying dogs that harmed residents.

The officers worked at the Antioch and Pittsburg Police Departments in the Bay Area, where Ismail Ramsey, the U.S. attorney for California’s Northern District, said in a news conference that the officers had “acted as though they were above the law.”

Prosecutors painted a picture on Thursday of two police departments in deep disarray, with officers skirting accountability by destroying records and not wearing body cameras — actions that officials described as dishonest and dangerous.

Officers from both departments face maximum sentences of 10 to 20 years in prison and $250,000 fines.

“This will go down in history as one of the darkest moments in this city,” Lamar A. Thorpe, the mayor of Antioch, said in an interview. Mr. Thorpe was himself a target of some of his former officers’ antagonism: Some said in text messages obtained by the F.B.I. during its investigation that they wanted to shoot him, he said.

The Antioch Police Officers Association said in a statement that it looked forward to seeing the legal process play out and that it was “committed to still providing quality service to the citizens of Antioch and also providing support for our members who are still working through this difficult time.” The police department in Pittsburg, which abuts Antioch, did not immediately respond to calls seeking comment on Thursday.

Michael Rains, a lawyer for one of the officers charged in the case, did not immediately respond to a call seeking comment on Thursday. It was not immediately clear if the other officers had lawyers, and calls placed to numbers listed as belonging to some of them were not immediately returned on Thursday night.

Prosecutors laid out the indictments in four parts. Some officers were charged in two indictments.

The first part was described as a “college degree benefits fraud” that two officers from the Antioch department and four officers from Pittsburg had participated in. The fraud involved officers’ claiming that they had earned college credits toward degrees when really, according to court records, the officers had hired people to attend classes and take the exams for them.

The departments would reimburse tuition costs and award salary raises to officers who earned college degrees, Mr. Ramsey said. Those officers were charged with wire fraud and conspiracy to commit wire fraud.

The second indictment states that two Antioch officers conspired to distribute anabolic steroids, with one of them agreeing to destroy evidence of the illegal conspiracy.

One Antioch officer is accused in the third indictment of destroying, altering and falsifying records in an effort to obstruct a federal investigation. The officer is also charged with a civil rights violation for grabbing a person’s phone and damaging it to prevent the retrieval of evidence, Mr. Ramsey said. That officer is charged with deprivation of rights, obstruction of official proceedings and destruction or alteration of records.

The fourth indictment was described by Mr. Ramsey as a “disturbing litany of civil rights violations by three officers of the Antioch Police Department.”

The 29-page indictment describes how three officers boasted about their illegal use of force in text messages with one another.

One officer who worked with a dog took photographs or videos of a person’s injuries from a dog bite and shared them on his personal cellphone with officers who had not been involved in the episode. On Dec. 19, 2019, he wrote: “I’m gonna take more gory pics. gory pics are for personal stuff. cleaned up pics for the case.”

Another officer also took photographs of injuries on people whom he had attacked with a firearm that fires less-lethal ammunition.

He would then gather the spent ammunition “to create a display,” telling other officers that he was making a “mantle” and a trophy flag from the material, the indictment states.

Mr. Ramsey said the 10 officers had violated their duty to enforce laws and protect the public.

“When this happens,” he said, “the damage done to the public trust cannot be easily calculated.”

Representative Mark DeSaulnier, whose district includes Antioch and Pittsburg and who has called for the Justice Department to investigate the Antioch Police Department, described the actions of the officers in one word in an interview on Thursday night: “Shocking.”

Robert Tripp, the special agent in charge of the F.B.I. field office in San Francisco, said at the news conference that none of the officers arrested on Thursday “were actively engaged in law enforcement, although three were current employees of local departments who had been placed on administrative leave.”