The authorities found pictures of child pornography on the Senator's phone after executing a search warrant on Folmer's home in Lebanon, Pennsylvania on Tuesday.
CNN has asked Folmer's office for comment.
An investigation was initiated after a notice reported that Tumblr had found a user who had uploaded a child pornography image with the application. More investigations led to Folmer's house, it was said.
"This defendant serves as a state senator and was commissioned to honor and represent his community in the Pennsylvania Capitol," Shapiro said in a statement.
Folmer was charged on Tuesday with sexual abuse of children, possession of child pornography and criminal use of a communication device.
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In a joint statement, Pennsylvania Senate President Pro Tempore Joe Scarnati and Senate Majority Leader Jake Corman said that Folmer would immediately be dismissed as chairman of the Senate Government Committee.
"We are shocked to hear of the allegations against Senator Folmer tonight," the statement said. "We will fully cooperate with law enforcement agencies in this most disturbing matter."