A twisted Pennsylvania school resource officer was arrested Wednesday for allegedly pressuring a 14-year-old student into a sexual relationship and molesting her during a school dance he was chaperoning.

Costas Nick Alestas, 43, is also accused of sneaking a disturbing up-the-skirt video of an 11-year-old girl as she walked down the hallway at East Hills Middle School in Bethlehem.

Alestas’ alleged abuse came to light last month when the teenager confided in a guidance counselor about the weeks-long relationship, officials said.

Her mother had previously found a trove of dirty text messages between the pair, but Alestas — who was also the school’s co-ed soccer coach — tried avoiding capture by using a second phone number, the Bethlehem Police Department said Wednesday.

“There was deceptive behavior trying to mask who the text messages were from,” Bethlehem Police Chief Michelle Kott said at a press conference.

The teenager quickly gave him up when investigators questioned her, saying he had given her his personal phone number while they were on school grounds.

“The communication with Alestas included conversations about engaging in sexual acts. As the communication between Alestas and the victim continued, the interactions progressed into several encounters involving sexual contact between the two,” the department said in a release. 

The perverted encounters allegedly took place both during the school day in his office and after school inside Alestas’s car, police said.

One horrifying incident even occurred “during a school dance while Alestas was on duty and in police uniform.”

That same day, the disgraced school cop also allegedly filmed the video of the second, 11-year-old victim, which was recovered when investigators combed through his phone.

An analysis of Alestas’ phone showed about 4,980 messages exchanged with the 14-year-old, and 49 phone calls, since March 26, according to a police affidavit obtained by Lehigh Valley News.

The arrest came as a shock to the Bethlehem Police Department, who said Alestas was a respected six-year veteran of the department.

“There was no indication that this was going on or that this individual had engaged in any of this behavior. He was well-liked at the school. He had received awards of merit and the past. So this comes as an absolute shock and surprise,” Bethlehem Police Chief Michelle Kott said.

Alestas was immediately placed on administrative leave and has been charged with several felony offenses, including statutory sexual assault, institutional sexual assault and invasion of privacy.

Court records show Alestas was unable to post bail and remains in the county jail.

Alestas became the second school resource officer in Northampton County to be arrested and charged with allegedly carrying out an inappropriate relationship with a student in the last few weeks.

Ex-Easton Area High School officer John Smoke was busted last month after he allegedly “sent explicit photos to an underage student.”

“We need to start talking about whether there’s prophylactic measures. We can take as far as policy and procedures that can lessen opportunities for this kind of behavior,” Northampton County District Attorney Stephen Baratta said Wednesday.