High-tech drones were deployed, hundreds of hours of video were examined and state-of-the-art tools scrutinized an “enormous amount” of forensic evidence. But when an arrest came in relation to the high-profile killing of UnitedHealthcare CEO Brian Thompson, it boiled down to “good old-fashioned police work,” authorities said.

Five days after Thompson was brazenly gunned down on a sidewalk in Midtown Manhattan, 26-year-old Luigi Mangione was identified as a “person of interest” in the homicide that NYPD Commissioner Jessica Tisch said “captured the attention of the entire nation.”

Mangione, a former high school valedictorian with no known criminal record, was taken into custody Monday morning at a McDonald’s in Altoona, Pennsylvania, about 100 miles east of Pittsburgh, after an employee recognized him from surveillance photos that the NYPD released of the gunman and called 911.

He was subsequently charged with five crimes, including carrying a gun without a license, forgery, falsely identifying himself to authorities and possessing “instruments of crime,” according to a criminal complaint released Monday night.

Altoona police officers responding to the employee’s tip confronted Mangione as he was eating at the fast-food restaurant, investigators said.

“Upon further investigation, officers recovered a firearm on his possession, as well as a suppresser, both consistent with the weapon used in the murder,” Tisch said.

Mangione — who grew up in Maryland and had later lived in both San Francisco, California, and Honolulu, Hawaii — was charged with firearms possession, in addition to other charges, but has yet to be charged with Thompson’s murder, Tisch clarified.

NYPD Chief of Detectives Joe Kenny described the weapon allegedly found on Mangione as a “ghost gun” that appeared to be made with a 3-D printer and was capable of firing 9mm rounds.

Mangione was also in possession of a three-page, handwritten document that Tisch said “speaks to both his motivation and mindset.”

Kenny added that the document contained writing that expressed “some ill will toward corporate America.”

Multiple fraudulent IDs were found on Mangione, as well as a U.S. passport, Tisch said.

“Also recovered was a fraudulent New Jersey ID matching the ID our suspect used to check into his New York City hostel before the shooting incident,” Tisch said.

Kenny said that prior to Mangione’s arrest, police had not identified him by name.

Tisch said that during the investigation, police deployed drones, K-9 units and SCUBA divers. She said investigators also leaned heavily on the expertise and technology of the FBI, in addition to its own intelligence and counterterrorism bureaus, to help crack the case.

“For just over five days, our NYPD investigators combed through thousands of hours of video, followed up on hundreds of tips and processed every bit of forensic evidence, DNA, fingerprints, IP addresses and so much more to tighten the net,” said Tisch. “Our detectives also went door to door interviewing potential witnesses and doing good old-fashioned police work that our investigators are famous for.”

The commissioner added, “This combination of old-school detective work and new-age technology is what led to this result today.”

Thompson’s killing unfolded around 6:40 a.m. on Wednesday outside the New York Hilton hotel where the executive was to attend a shareholder meeting.

The gunman, who was wearing a mask and a hooded jacket was captured on surveillance video ambushing Thompson from behind in what investigators described as a “brazen and targeted shooting.”

Kenny said the big break in the investigation came within hours of the probe commencing, when police obtained a surveillance photo of the suspect at a Starbucks at West 56th Street and 6th Avenue near the New York Hilton.

“There’s numerous lynchpins in this case, in the fact that we’ve recovered an enormous amount of forensic evidence, an enormous amount of video. So, I really couldn’t put it on one thing. But if I had to, it would be the release of that photograph,” Kenny said. “We took that photograph and we asked for the public’s help in identifying this subject, and the public responded.”

Kenny said detectives spent hundreds of hours combing through “every source of video that we could collect.” Using video, detectives were able to track the killer from the scene of the shooting as he made his getaway on foot and on bicycle through Midtown Manhattan, Central Park and upper Manhattan. Detectives even obtained video of him soon after he arrived in the city by bus.

Police subsequently released clearer images of the suspect, including one in which he showed his face while checking into a youth hostel in upper Manhattan, and an up-close shot of him in the back of a taxi wearing a mask.

“The images that we shared with the public were spread far and wide, and the tips we received led to the recovery of crucial evidence,” said Tisch, acknowledging the “instrumental role of the media and the public in this case.”

Tisch added, “We should never underestimate the power of the public to be our eyes and our ears in these investigation.”

She said it marked the third time in as many weeks that a tip from the public led to an arrest in a high-profile case, including a triple stabbing homicide in Manhattan and a series of gunpoint robberies in Queens, during which a police officer was shot.

Kenny said the investigation is far from over, as detectives continue to look into whether the gunman had help.

“We believe, at this point, our investigation is leaning toward he acted alone,” Kenny said.

Looking ahead, Tisch said, “We’ll work out through extradition to bring him back to New York to face charges here, working with the Manhattan District Attorney’s Office.”