Federal officials say that on Tuesday, a California engineer admitted that he blew up two Pacific Gas and Electric transformers in 2022 and early 2023.

Authorities say Peter Karasev, 38, blew up two PG&E transformers in San Jose with homemade bombs, which did a lot of damage and knocked out power to many people.

Police say the crimes happened in two different places in December 2022 and January 2023. Prosecutors say that during the first bombing, nearly 1,500 people were without power for almost 16 hours. Prosecutors say the second attack damaged a generator and a building next to it, cutting power to dozens more homes and businesses.

When Karasev was arrested in March 2023 and his home in San Jose was searched, detectives said they found a “staggering trove” of explosives and dangerous materials. Prosecutors said they found more than 300 pounds of dangerous chemicals, guns, explosive materials, and remote detonation devices in his home, car, and office.

The Department of Justice said that Karasev admitted that the attacks were “planned and deliberate” when he pleaded guilty to two counts of willful destruction of an energy plant on Tuesday.

Judges said he would spend between 8 1/2 and 10 1/2 years in federal jail as part of his plea deal. He also agreed to pay at least $104,076.26 to fix the problems he made. His punishment hearing is set for August 19.

ABC News tried to get a word from his lawyer but did not hear back right away.

Acting U.S. Attorney Patrick Robbins for the Northern District of California praised how quickly police worked to “prevent further harm” to people in San Jose.

Robbins said in a statement Tuesday, “There can be no mistake about the amount of damage that could have happened.”

When Karasev was first charged with several federal crimes in October 2023, he pleaded not guilty. However, on Tuesday, he changed his plea and admitted to the two counts, according to court records.

He is also being charged by the state with bombs. Court records show that he will next be in court in Santa Clara County in June.

Karasev was a software engineer at a business that makes self-driving cars when he was caught.