Ulloa decommitted from Stanford on January 13th, three months to the day after giving his pledge to David Shaw that he would be coming to Palo Alto.
When he decided to pursue other options, Arizona came right in, offering a scholarship on the 18th, and sending new defensive coaches Marcel Yates and Donte Williams out to Ulloa's house just a couple days later. Ulloa then visited Tucson on the 22nd.
It seems to have come down to Arizona and Oregon for the highly-regarded safety out of Corona, CA. Ranked the 22nd-best player at his position, there's certainly a chance that under the tutelage of coach Williams, Ulloa will come in and make an immediate impact in the Arizona secondary.
Arizona needs playmakers at safety, and that's exactly what they'll be getting here, as you can see in his highlight video.