Moore had prominent firearms lawyer Evan Nappen on speaker- phone before he even got back to his home in Carneys Point, Salem County.
"After a while of them threatening to take my kids, get warrants and intimidation they left. Empty handed and seeing nothing," Moore wrote. "People it can happen that fast. Most people wouldn't have stood up to them like I did."
Moore's story spread quickly to the Blaze, a conservative news site founded by former Fox News host Glenn Beck - where Moore, a self-described libertarian, was commended for his stance.
Carneys Point Police Chief Robert DiGregorio declined to comment on the incident but said his department was still investigating with assistance from the Salem County Prosecutor's Office. The prosecutor's office did not return a phone call for comment.
DiGregorio said the police report would help explain the matter, but that report was not made available Tuesday.
The gun in the photo resembles an AR-15, the same weapon Adam Lanza used when he stormed Sandy Hook Elementary School in Newtown, Conn., in December and mowed down 26 children and adults. Nappen said Moore's gun is actually a smaller, .22-caliber rifle that holds fewer rounds, designed to resemble an AR-15-style rifle.
Bryan Miller, of the gun-violence group Heeding God's Call, said it's understandable that someone grew concerned over the photo of Shawn Moore's son holding the rifle. "Looking at the photo, it's impossible to tell by sight that the gun is not an assault weapon," Miller said.
According to New Jersey law, a child younger than 18 can possess a gun only under "direct supervision of his father, mother or guardian, or some other person who holds a permit to carry a handgun or a firearms purchaser identification card."
Moore, a National Rifle Association-certified firearms instructor and range-safety officer, bought the gun so that he and his son could target-shoot together, and it is kept in a safe when not in use, Nappen said.
"This was his birthday present," the lawyer said. "This is father and son bonding."
Nappen said DCF still wants to see Moore's guns, but he said that's "not going to happen." Kristine Brown, a DCF spokeswoman, said she couldn't comment on the incident, but added that her office is required to follow up on any allegation made to a tip line.
On Twitter: @JasonNark