Gene Bush, 52, was being held Monday at a county jail and was expected to make an initial court appearance Tuesday.
He was arrested late Friday by campus police after he allegedly shot at a traffic light a block away from the university. Police searched him, his van and a storage unit, finding weapons, ammunition and what police called an anti-government manifesto.
"Given the situation, with the amount of guns and ammunition involved, we thought it best that he remain in custody until we know the full story behind him," said UCLA police Sgt. Phil Baguiao. "We would consider him a danger to society given the circumstances."
Police said officers found Bush carrying the pistols - which were equipped with laser sights - and 400 bullets. They also found another 7,800 rounds of ammunition in his van and 3,000 more in his storage locker, police said.
A press release said Bush appeared to have no criminal history and was living out of his van.
After his arrest, Bush made anti-government statements and told police to look in his nearby suitcase for "the secret," the release said. A Los Angeles police bomb squad found timers, paint thinner and other suspicious items inside, as well as his manifesto.
UCLA police spokeswoman Nancy Greenstein said police believe Bush was acting alone and didn't have a specific target. "He had writings and a lot of them seemed to be anti-government, talk about 9/11," she said.
It wasn't immediately clear why police didn't announce Bush's arrest until Monday, more than three days after the incident. It wasn't known if Bush had retained an attorney.