Kyle Thompson is accused of taking a girl into these woods behind his Burtonsville, Md., apartment and molesting her in 2013. (Dan Morse/TWP)

The claim by a confidential source was stunning: A 31-year-old man, quietly living in Burtonsville, Md., had sexually assaulted three young children — attacking at least one in the woods behind his apartment — and video-recorded the acts.

The day after hearing the accusation, police armed with a search warrant entered the man’s apartment and spotted computers and digital storage drives.

Videos and photographs pulled from the devices, according to Montgomery County police allegations filed in court, now are at the center of a growing investigation into Kyle Stephen Thompson, a commercial HVAC technician who maintained cooling systems at office buildings and large data centers in the Washington area.

Police say the videos show Thompson sexually assaulting a girl younger than 5 who was tied with a belt and calling for “Mommy.” Another video, according to the police allegations, depicts Thompson molesting a different girl, also younger than 5, as she cried.

The alleged abuse occurred at various times over the past two years, police affidavits state.

Kyle Thompson, 31, has been charged in Montgomery County with sex abuse counts for alleged incidents stretching back four years. (Montgomery County Police)

Detectives also suspect that sometime in 2013, Thompson molested a slightly older girl in the woods near a small pond and creek, according to court records.

“The allegations,” Montgomery Assistant State’s Attorney Danielle Sartwell said in court recently, “are, quite frankly, just horrific.”

Thompson was charged on March 17 with two counts of first-degree sex offense, two counts of sex abuse of a minor, and one count of third-degree sex offense, according to court records. He was charged March 29 with additional counts of sex abuse of a minor and third-degree sex offense. He remains jailed on no-bond status.

In court filings, Montgomery County police said the FBI is conducting a child pornography case in connection with the allegations. Dave Fitz, a spokesman for the FBI’s field office in Baltimore, said FBI agents have been assisting Montgomery County police in the investigation of Thompson to see whether federal charges might apply.

“We believe he befriends women who have young girls in order to have access to them,” said Capt. James Humphries, commander of the Montgomery Police Department’s Special Victims Investigation unit.

His detectives also determined that Thompson had 15 registered firearms, according to court records, and alleged that he threatened to harm at least one person who knew one of the young girls.

On March 17, after being taken into custody, Thompson said little to detectives, according to court records. “Thompson denied everything,” Detective Melvin Avelar wrote in an arrest affidavit.

Thompson has not yet had a chance to present an account in court, and his current attorney, Isabelle Raquin, could not be reached for comment.

Thompson’s employer said he was “shocked and saddened” by the allegations when he learned of them two weeks ago.

“We never had any reason to suspect he was anyone but a hard-working, loyal employee,” said Lee Piazza, vice president of Virginia-based Compu Dynamics, a commercial air-conditioning firm that specializes in cooling data centers at private companies and government buildings.

Piazza said Thompson came to the company about 10 years ago, having passed a background check that included a criminal record screening.

Thompson was terminated from Compu Dynamics about two weeks ago, according to Piazza.

The apparent lack of a criminal record appears consistent with information gathered by county jail officials and by John Lavigne, an attorney who represented Thompson in a March 20 bond review hearing after Thompson’s first set of charges.

“Absolutely no prior record,” Lavigne told a judge about Thompson.

Court records show that when Thompson was booked into jail, he reported making $80,000 annually as an HVAC technician.

“He just kind of started that after high school, worked his way up, and now holds a masters license in that field,” Lavigne said in court.

The police case against Thompson began March 16, according to court records, when detectives spoke to their initial source whose name they did not disclose in filings to the court.

That source told police Thompson had shown the source several videos of Thompson performing sex acts on three underage girls, according to court records. Detectives said in their court filings that they were able to corroborate an alleged incident involving one reported victim. A day later, they apprehended Thompson when he was away from his home and then searched his apartment.

In Thompson’s Burtonsville neighborhood, word spread about the search.

“He was very pleasant,” neighbor Donna Ballard said.

At Thompson’s court appearance March 20, Sartwell, the prosecutor, urged District Judge Eugene Wolfe to hold Thompson on no-bond status, citing the age of the victims and the firearms found at his home.

Wolfe ordered Thompson held without bond.

Standing outside her front door Tuesday, Ballard said Thompson had moved to the neighborhood about a decade ago. He seemed shy at first, she said. One day he saw her while she was outside and said he had noticed a dead bird inside the outdoor equipment of her air-conditioning system. “Do you want me to get it out for you?” he asked, and he did, according to Ballard.

Ballard said she was struggling to reconcile the allegations in the charges with her interactions with Thompson.

“It’s hard — when you see just one side of a person — to comprehend this sort of stuff,” she said. “I don’t think any of us can sit in judgment until all the facts come out. But if he did this, he needs to be locked up.”