Sen. Leland Yee, D-San Francisco, a strong advocate of gun control, said he received an email four weeks ago from someone claiming to be a sniper and vowing to assassinate him in the Capitol if he didn't drop his efforts.
"His email detailed in a rather specific way certain weapons he possessed and exactly how he was going to kill me," Yee said at a news conference.
Yee said he turned over the email to security personnel at the Senate, who called the California Highway Patrol.
On Tuesday, federal and state officials raided two homes in Santa Clara County and arrested Everett Basham, 45. Authorities said they seized bomb-making material and weapons from one of the homes.
Basham has been charged with threatening a public official. It was unclear if he has an attorney.
Scott MacGregor, CHP chief of protective services, said he considered the threat to be credible and noted that dangerous, explosive chemicals were found during the search of the two homes connected to Basham. No further arrests were expected, MacGregor said.
Yee has received several racist threats before but nothing as detailed as the latest email, he said.
Yee said he has no intention of dropping or altering the bill he introduced related to guns.
"Neither this threat or any other threats is going to deter me from addressing the critical issues surrounding gun violence," Yee said. "This case is a rather troubling one, and only further demonstrates the need to address this particular problem."