AUGUSTA — For sexually assaulting a girl under age 12 in Vienna five years ago, a Brunswick man will spend the next 15 years in prison.

Patrick Logan Patterson, 26, pleaded guilty Monday at the Capital Judicial Center to one charge of gross sexual assault that occurred between June 1, 2011, and Nov. 30, 2012, in Vienna.

Justice Michaela Murphy sentenced Patterson to 15 years in prison followed by a lifetime period of supervision and said he must register as a lifetime offender under the Sexual Offender Registration and Notification Act. The sentence was recommended by both the prosecution and the defense.

“If you violate any conditions of lifetime supervision, you could come back to court and the court could sentence you to life in prison,” Murphy told Patterson. He said he understood.

The prosecutor in the case, Assistant District Attorney Kristin Murray-James, told the judge there were five incidents of sexual assault including oral sex and sexual intercourse beginning in the summer of 2011 when Patterson and the victim were in a tent together and the victim was under 12.

Patterson’s attorney, Joshua Klein-Golden, told the judge that the plea was part of an agreement that encompasses offenses that took place in Sagadahoc County and that the sentence is to be concurrent. The attorney said Patterson wanted to take responsibility for his actions.

Patterson is scheduled for a hearing 8:30 a.m. Nov. 9 in Bath on three counts of sexual abuse of a minor which allegedly occurred in June, August and October 2014.

Conditions of Patterson’s supervision include a prohibition on contact with girls under 16 except for immediate family members with adult supervision.

The victim told the judge on Monday, “Words can’t really express how this has changed my life.”

The girl said the experience affects her ability to learn and to trust people.

“I am here today to try to move past it and get this giant weight off my shoulders,” she said.

She said she was able to come to court and speak about the ordeal so that no one else would be victimized.

The girl also addressed Patterson directly, saying, “You messed up my mind. You told me really personal stuff that happened to you when you were little. Why would you put someone else through the same thing?”

A sister of the victim also spoke, calling Patterson “a monster” and “a predator” and saying she had walked in on one assault.

A grandmother of the victim spoke as well, telling Patterson, “You do not and will not have power over her again.”

Patterson apologized in court and said, “This stuff has been haunting me for a long time.”

He said he should have dealt with it sooner.

“I wish I could take back everything that I did,” he said. “I have been in the wrong. I know I need help. I know I need to go away. I don’t want to be that person any more.”

His mother addressed the judge as well, saying she hopes everyone gets the help needed.

Murphy told Patterson that she understood he was being brought to prison on Monday. Patterson had been free on bail until the hearing.