OAKLAND (BCN) — A federal judge has sentenced a Martinez man to 30 years in prison for traveling with the intent to engage in sexual acts with a teenager who went missing out of Oregon in 2014, prosecutors said on Wednesday.

Blake Robert Johnston, 42, will also have a lifetime of supervised release as part of the sentence delivered Tuesday by U.S. District Judge Jeffrey White in Oakland, according to the U.S. Attorney’s Office.

Prosecutors said after being indicted in April 2015, Johnston pleaded guilty on Dec. 1 to traveling with the intent to engage in illicit sexual conduct with a minor, admitting to making two trips to Oregon for encounters with a 14-year-old girl he met online.

The teenager from Salem was picked up by Johnston in October 2014 and driven back to the man’s Martinez home. After being reported missing, she was found by Martinez police in Johnston’s bed after investigators used mobile phone records and her computer history to determine her location, prosecutors said.

A hard drive seized in Johnston’s bedroom contained images and videos of at least 94 minors identified so far with whom Johnston had established online communications, according to prosecutors.

Of the underage victims, prosecutors said at least four met with Johnston and engaged in sexual activity with him.

Investigators determined that in Johnston’s communications with the victims, he encouraged them to commit harmful acts such as cutting themselves, strangulation and drug abuse, prosecutors said.

The judge, before delivering his sentence Tuesday, described Johnston’s behavior as “unusually heinous,” on a level the court “has never seen,” prosecutors said.

White said Johnston’s approach with his victims was to prey upon their low self-esteem with “extreme cunning, guile, intelligence, strategies and a lot of thought and a lot of skill,” prosecutors said.

The judge ordered Johnston to have no contact with victims or minors without the permission of his probation officer after his prison sentence. He must also register as a sex offender.

Johnston “sexually exploited an untold number of children to satisfy his demented fantasies,” Brian Stretch, acting U.S. Attorney for the Northern District of California, said in a statement.

Stretch said Johnston received “a just sentence we can only hope provides some measure of closure to the victims and their families who had to endure Johnston’s torment.”

The amount of victim restitution Johnston is being ordered to pay will be determined in court on June 28.