JOSHUA TREE, Calif. -

52 year-old Caleb Hesse of Joshua Tree is accused of committing sex crimes with young boys.

He was a first grade teacher at Friendly Hills Elementary in Joshua Tree.

But San Bernardino County Sheriff's investigators believe most victims were involved with a youth group at the Evangelical Free Church in Yucca Valley, where Hesse worked as a volunteer.

"We're absolutely crushed. We had no idea that this was going on," said Pastor Bill Wilcox.

Wilcox says Hesse went to him with a confession on Tuesday.

"Mr. Hesse called me Tuesday night and I met with him. He confessed a great deal and I agreed to go to the sheriff. It was very, very clear he needed to turn himself in and he was very willing to do that," said Wilcox.

It's believed Hesse abused kids during overnight trips. The pastor says they were not church-sponsored activities.

"What we know is these were trips he would take with boys and go up to the mountains and camp," said Wilcox.

Investigators say some victims could be 30 to 40 years old because the crimes span from the early 1980s -- when Hesse started as a church volunteer -- to as recent as a week or two ago.

"The investigators do believe that as the investigation continues that more victims will be identified in the coming weeks," said San Bernardino County sheriff's spokeswoman Cindy Bachman.

It's unclear if Hesse abused any students at Friendly Hills, where he taught for about 25 years.

The Morongo Unified School District said Hesse turned in his resignation wednesday.

"We're extremely concerned. The safety of our children is paramount in this district. We will do everything we can to assist all the families impacted by this event," said Assistant Superintendent Tom Baumgarten.

Hesse's bail was set at $2.5 million. He's expected to be arraigned on Monday.