Lewiston mass shooting gunman Robert Card’s body was found in an unlocked trailer with two firearms by his side as police said they’re now probing the “mental health component” behind the massacre.

Card, 40, was found dead from a self-inflicted gunshot wound in a trailer at the Maine Recycling Corporation in Lisbon at 7:45 p.m Friday, Department of Public Safety Commissioner Mike Sauschuck said at a news conference Saturday morning.

The recycling plant was previously cleared twice by authorities, who then returned to the site when the business owner alerted them to an overflow lot with additional trailers, Sauschuck explained.

“Nobody had any idea that across the street there was an overflow parking lot,” he noted.

Card had an “employment relationship” with the business, Sauschuck said, but declined to elaborate whether the Army Reservist was a current or former employee of the plant.

Card’s body was found in a trailer that was “unlocked from the outside,” and alongside two firearms.

“The one picture that I saw looked like he had the same sweatshirt on that he had in the [surveillance photo] that we put out [from] the bowling alley,” Sauschuck commented.

Authorities declined to give an exact time of death, pending autopsy results.

All three weapons — the two found with Card’s body and the one “long gun-style” firearm discovered Wednesday in the suspect’s abandoned Subaru -— “appear to have been legally purchased by him,” Lisbon Police Chief Ryan McGee confirmed.

“Some of them were … purchased very recently. And some of them [were bought] years and years ago,” McGee said.

Card also left behind a “paper-style note” addressed to a loved one that included his cell phone passcode and bank account numbers, Sauschuck continued.

“I wouldn’t describe it as an explicit suicide note but the tone and tenor was that the individual was not going to be around,” the commissioner said.

Previous reports indicated a note was found at Card’s home shortly after he was identified as a suspect in the deadly Wednesday night shooting.

Police now have a search warrant for Card’s cell phone and the bank accounts, according to Sauschuck.

The phone, in particular, may help law enforcement piece together how long Card plotted the shooting, as well as his movements in the hours before the incident.

Card was first pinged as the possible shooter after his own family members called to identify him based on the surveillance image police released Wednesday night, Sauschuck noted.

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“Our investigation would have been detrimental if they did not come forward immediately,” he said.

“They should be acknowledged in that. As a whole, we’ve found them very cooperative.”

Katie O’Neill, Card’s sister-in-law, previously told The Post her the family was “heartbroken” by the shooting.

“There is clearly a mental health component to this,” Sauschuck said of the mass shooting at Just-In-Time Recreation and Schemengees Bar and Grille.

Card suffered a psychological deterioration in the months before the killings, and spent two weeks at a mental health facility after threatening to “shoot up” an army base, according to relatives.

Even so, authorities do not have access to any records that indicate the father of one was forcibly committed, Sauschuck explained.

When pressed on why Card’s history of mental health issues were not pinged by Maine’s yellow flag law — which allows police to petition a judge to temporarily prohibit a person from possessing firearms if they are a danger to themselves and others — Sauschuck said the law’s criteria is “very specific.”

“[It’s] about an individual that’s in protective custody with law enforcement to begin with,” Sauschuck said.

“And, do we have probable cause to believe that they are in possession [of guns], or that they could be in possession of dangerous weapons? So if we meet those criteria, then you can take an individual in for a yellow flag assessment and weapons restriction assessment. And at that time, your criteria changes from a likelihood of serious harm to the likelihood of foreseeable harm.”

Card had no criminal history aside from a single 2007 charge for operating under the influence, McGee said.

Meanwhile, Lewiston, Lisbon, and the surrounding areas were starting to revive Saturday morning after the two-day manhunt for Card forced residents to shelter in place through the end of the week.

Locals attempting to drop off their garbage at the Lisbon Transfer and Recycling Center, which is near the center where Card’s body was discovered, were turned away as law enforcement continued to comb the scene.

“I’m just happy they caught him. It could have been a lot worse” a man who gave his name as Bob, 85, told The Post.

“I had a feeling when I saw the car on the boat ramp. I said he offed himself,” the former police officer said, referring to the discovery of Card’s Subaru at a boat launch not long after the shooting.

Eighteen people were killed and 13 others injured when the killer opened fire at the bowling alley and then the bar Wednesday evening.

“I’m surprised they found him… I’m glad it’s over. I feel so sorry for the poor people who lost their family,” Litchfield resident Melvina Wheeler, 77, told The Post after shopping at the Lisbon flea market.

“I’m just trying to keep a smile on my face. It’s hard. My heart really is sad but I’m trying,” she continued.

“I was trying to be safe. I stayed home. There weren’t many people out.”

Three of the survivors remained in critical condition Saturday, according to Sauschuck.