Bull was arrested around 2 p.m. in his home in Lake Forest. He allegedly told investigators that he viewed child pornography on a daily basis.
Authorities started investigating Bull in June after receiving a tip from a father in Arizona. The father was concerned his 13-year-old son was chatting online with a person, later identified as Bull.
Bull used the screen name "joeycal."
The conversations allegedly involved graphic language.
Authorities allege they found sexually explicit photos of boys between 8-12 years old on Bull's computer. They also allege there were images of child porn and pictures of minors who may have had contact with Bull.
Authorities suspect photos of three unidentified boys, possibly from Orange County, were taken in Bull's bedroom and living room. The photos allegedly show Bull and an unidentified elderly man with the children, wearing bathing suits. Investigators allege these pictures show Bull with his arms wrapped around the boys' torsos while they are sitting on his lap.
Authorities say those photos are not pornographic, but along with other evidence, they do raise concern.
"The pictures that we've seen show physical contact between an unrelated adult male and children 12 and under. When you have contact like that, that's something that raises our concerns. Based on the messages he was sending to the child in Arizona, and then what's on your computer, indicates, thus, that we have somebody who has possibly got more victims out there that we don't know about," said Kevin Blair, Federal Bureau of Investigation.
Authorities say Bull was involved with the American Youth Soccer Organization in Orange County. He was a soccer coach, youth referee coordinator and an AYSO board member. Bull also told investigators that he is a substitute teacher at Esperanza High School in Mission Viejo where he helped special-needs children of all ages.
If you know of any potential victims you are urged to call the FBI at (310) 477-6565.
The FBI also hopes to find those three boys and the unidentified man in the pictures found at Bull's residence.