OAKLAND -- A Hayward man has been sentenced to 17 years in prison after being found with hundreds of graphic images of children and exchanging email messages with other adults expressing a "desire to commit extreme violence against a child," according to the U.S. Department of Justice.

Terry Howell, 57, was arrested last September and charged with distributing child pornography to a person in another state via email. At the time he was arrested, Howell's cell phone contained over 80 videos and more than 550 images showing minors engaging in sexually explicit conduct, including minors being subjected to sadistic conduct, according to the indictment.

Howell, who also used the alias of Kevin Kramer, had prior convictions for sexual offenses against a child, increasing his jail time.

"This case should serve as a stern warning to those who mistakenly believe cyberspace affords them anonymity and they can use the Internet to sexually exploit children with impunity," said Tatum King, acting special agent in charge for Immigration Customs Enforcement's Homeland Security Investigations, in a prepared statement.

"Online predators should be on notice that ICE will do everything in its power and use every tool at its disposal to track them down and ensure that they are brought to justice."

Follow Karina Ioffee at Twitter.com/kioffee.