A sharp-eyed Nassau cop foiled what could have been a $20 million heist from a Hicksville armored car company, arresting a fleeing parolee with some of the loot in his car, officials said Thursday.

Authorities said a group of thieves armed with sledgehammers, a hydraulic jack and other tools broke into the vault at the Loomis Armored Inc. warehouse on the night of Aug. 16.

"These individuals were not amateurs," said acting Nassau Police Commissioner Thomas Krumpter. "It's clear this burglary was interrupted."

Krumpter announced a $25,000 Crime Stoppers reward for information leading to the arrests of other suspects in the burglary.

The parolee, Edgar Medina, 53, of Brentwood, was arrested about 10:20 p.m. in New Cassel with $1.8 million in the trunk of his rented sedan after a brief police pursuit.

According to court papers, Medina told the arresting officer: "I used a crowbar. It's at the armored place."

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Krumpter called Medina a "career criminal" with at least eight felony arrests on his record, including weapons possession, during a news conference Thursday at police headquarters in Mineola.

Medina, who wasn't armed at the time of his arrest, was charged with third-degree burglary, first-degree grand larceny and possession of burglar tools.

He's being held in jail in lieu of $300,000 bond, according to online court records.

An attorney for Medina could not be reached by phone or at her office.

The night of the burglary, an officer from the Second Precinct saw Medina's Volkswagen Jetta -- its trunk open -- parked outside the Alpha Plaza warehouse and approached, said Nassau Chief of Detectives Kevin Smith.

Medina saw the officer coming "and appears to go and throw something in the trunk, and starts to slam the trunk door," Smith said. "The trunk never shuts, though.

"As the officer says 'What are you doing?' . . . [Medina] gives some lame excuse, and then the officer says 'What about the bag I just saw you throw in the trunk?' And the guy jumps in the car and he takes off," Smith said.

The officer pursued Medina "for less than a minute," Smith said. "At that point, the guy appears to give up."

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Police said they are unsure how the other thieves managed to avoid arrest.

In video security footage from the scene, masked men appear to survey the area before the burglary and disable an alarm system, Smith said.

"It appears they were casing the place. . . . They seem to be looking at the wires that are surrounding the outside of the place; they seem to be looking for, choosing, perhaps, their access point into the building," he said.

Police said they are looking for two to four suspects, but declined to elaborate.

The identity of the arresting officer, an eight-year veteran, was withheld, with officials citing the ongoing investigation.

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"There's a lot of money involved. There's still other individuals at large," said Deputy Insp. Gary Shapiro, a department spokesman.

Officials, however, heaped praise on the police officer.

Acting District Attorney Madeline Singas called the officer's work "astute and observant" and added: "I would like to commend this police officer for his quick thinking, for his quick action and for foiling this very sophisticated and brazen burglary."

James Carver, president of the Nassau Police Benevolent Association, said, "This is just another great job by our police officers."

Carver said the officer would, in the future, "absolutely" receive the joint PBA-county legislature "Top Cop" award.

Asked whether police think the Loomis burglars had assistance from someone with inside knowledge of the facility, Krumpter would only say that the investigation is continuing.

He declined to provide details about the security system breached by the thieves.

Danny Peck, Loomis' senior vice president for risk management, declined to comment, saying he didn't want to jeopardize the investigation.

"We're very pleased with the officer's response -- there's no question about that," Peck said. "We've been fortunate in that respect."