Christmas Eve was thought, by a decorated marine from Louisiana, to be the perfect day for a romantic encounter with a 13-year-old girl he met online.

Lance Cpl. Johnathan Plaisance, 20, based at North Carolina's Camp Lejeune and the member of the 2nd Intelligence Battalion was arrested in Harrisburg on Tuesday after the girl’s parents reported her missing on Christmas morning.

According to police authorities, Plaisance was communicating with the 13-year-old girl online for some months. He brought her a diamond engagement ring. Police Cmdr. Thomas Stangrecki said that Plaisance probably thought she was 15, Houston Chronicle reports.

Girl’s mother reported her missing around 8:45 a.m. Tuesday, after she has seen her the previous night.

Lt. Kevin Kraus said: “We had information from a sibling in the house that she was gathering some makeup at approximately quarter to 1.We also obtained phone records from the land line in the house. There was a suspicious number at approximately 12:34,” the Pitssburgchannel.com quotes.

After the call the girl took a cab to a Holiday Inn off Route 28 in O'Hara Township and met with the marine.

The two spent the night a motel and in the morning left together to board a Greyhound bus to North Carolina.

Police found about their relationship after they examined the family computer and the account of the girl on MySpace.com.

Police was joined by the FBI who helped them to track the pair to the bus station in Harrisburg.

Police arrested Plaisance on Tuesday night on felony charges of interfering with custody of a child and concealing of a child.

The girl was brought home by the FBI after she was examined at a Harrisburg hospital.

Kraus said: “We've learned that, during this encounter, he did propose to her and she did accept.”

After the FBI ends the investigation the case will be transferred to U.S. District Court in Pittsburgh.

Marine Corps said that it was cooperating with the investigation and all the questions were deferred to Pittsburgh police.