William Cottrell, 23, used an alias when he e-mailed The Los Angeles Times, claiming to be a member of the eco-terrorist group Earth Liberation Front and offering specific details to prove his involvement in the firebombings, the FBI said.
"The FBI hasn't seemed to pick up on any of them (clues), which makes this whole ordeal rather boring for us, the true culprits," one e-mail boasted, the FBI said in an affidavit.
Authorities searched Caltech classrooms and tracked the e-mails to Cottrell, a grad student in the physics department, according to the affidavit. They also seized six computers from the campus.
Cottrell was arrested for investigation of arson and vandalism. He was ordered held without bail at a court hearing. If convicted, he faces a maximum of 40 years in prison, the U.S. attorney's office said.
"The charges are unfounded," defense attorney Stephen Alexander said outside court.
Cottrell's father described his son as bright, hardworking and somewhat eccentric but incapable of the acts alleged by the government.
"We were hopeful he wouldn't be charged," Dr. William Milnes Cottrell said from his Concord, N.C., home. "We are very unhappy about it. We are still reasonably sure he wasn't a primary agent in this deed."
Prosecutors estimate the total damage was about $2.3 million.
"Those who set fires, like those at the Hummer dealership in West Covina, are misguided zealots," FBI Assistant Director Richard Garcia said in a statement.
The firebombing spree hit four car dealerships and at least four privately owned vehicles in communities east of Pasadena, where Caltech is located and where Cottrell was arrested.
The West Covina attack destroyed or damaged 72 vehicles, mostly SUVs, and a parts warehouse.
The Los Angeles Times reported that the e-mails the newspaper received began several weeks after the attacks, when the FBI arrested an environmental activist named Josh Connole in connection with the fires.
"Hello, the police have the wrong man here — I was amongst those responsible for the SUV attacks," read the first e-mail sent to the Times.
Connole was released without charges four days after his arrest. Connole told the Times that he hoped Cottrell's arrest would end any doubts about his innocence.