The early-morning arrest in Santa Monica of James Wesley Howell, 20, came just a few hours after at least 50 people were shot and killed in a gay nightclub in Orlando Florida, though authorities said they had found no evidence of a connection between the suspects.
Residents called police to report suspicious behavior from Howell, who was parked facing the wrong way in a white sedan, police said.
When officers arrived they saw an assault rifle sitting in Howell's passenger seat, Santa Monica police Lt. Saul Rodriguez said.
That prompted them to search the whole car. They found two more assault rifles, high capacity magazines and ammunition and a five-gallon bucket with chemicals that could be used to make an explosive device, police said.
Santa Monica police Chief Jacqueline Seabrooks tweeted that Howell told officers after he was arrested that he wanted to harm the gay pride event in West Hollywood that was taking place about seven miles away later Sunday.
Authorities would answer no further questions on Howell or his motives. The FBI has taken over the lead of the investigation from the local police.
At the scene, police spent the day searching the white four-door Acura sedan still parked facing the wrong direction on a busy thoroughfare in a mostly residential area of the seaside city west of Los Angeles. There was a red plastic gas can near the car and items laid out on a white sheet next to it.
Heriberto Gomez, a lifelong resident who says he watches over the neighborhood, stepped outside at 3 a.m. Sunday and saw the car in the street.
Gomez said the man then ran across the street and hid in bushes and overhanging trees. It appeared the man was looking back at him.
"I was looking at him for a minute, for a long minute," Gomez said. "He didn't want to come my way because he seen me standing right here."
The organizers of the Pride event said in a statement before the parade that "we are heartbroken that so many of our brothers, sisters and allies were lost in this tragic attack." Organizers said the tragedy made them all the more determined to continue with plans with heightened security from the Los Angeles County Sheriff's Department heightened security.
"Our brave founders made this happen to show the world who we are," the statement said. "We will be loud. We will be proud, and we will celebrate in honor of all those lost."
Taylor Hudson drove up from San Diego to attend LA Pride with friends. He followed news of the Santa Monica arrest on social media but then decided to ignore his phone and focus on the festivities.
"Everyone has Florida on their minds, in their hearts," Hudson said. "I just hope we don't have to worry about that kind of thing here."
Carl Oliver of Los Angeles attends the parade every year. He said he cried after hearing about Orlando but never considered not coming.
"This is about love," he said. "We have to show our love and unity."