An Oceanside man got a shock Wednesday by the content of a UPS delivery — a semi-automatic rifle — and a second jolt Friday when he learned its price.

“Wow, I should have kept the sucker,” said Joel Berman, 66.

Nassau police said it’s a 50-caliber Barrett rifle worth about $10,000.

“It’s more of a collector’s item,” said Det. Lt. Richard LeBrun, the department’s chief spokesman.

Berman and his wife had been expecting a toy airplane ordered from Kohl’s for a relative’s son, and while the sender on the UPS label said it came from Kohl’s and was 3.4 pounds, the package weighed 51 pounds.

The couple opened the keyboard-sized hard case Wednesday night in front of their 6-year-old granddaughter, wondering how it could be the Kohl’s toy, meant for the son of a friend.

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“Her mouth popped open,” the grandfather said. “We had to explain to her Santa delivered the wrong thing.”

Cradled in foam was a semi-automatic rifle with a sophisticated scope, a pistol grip, a stand, an ammo magazine and a copy of an Arizona man’s driver’s license and his concealed-weapons permit, Berman said.

In a photo taken by Berman, the UPS label, which had Kohl’s in Ohio as the sender, can be seen pasted over another UPS label from the Arizona resident to a gunsmith in upstate Woodbourne.

UPS officials on Friday apologized for the jarring mix-up and said they still do not know how the mistake was made.

“This is a highly unusual incident, and we are investigating what may have happened in our network,” said UPS spokeswoman Susan Rosenberg. “We are working with the [gunsmith] to make sure they receive their original order before the holiday.”

The rifle, which was on its way for repairs, was shipped properly after company regulations for sending weapons, Rosenberg said.

Since the story came out, Berman said he hasn’t been able to work because his time has been consumed by turning down media interview requests, from CNN and the four other news vans parked outside his home at one point.

All day, online gun rights sites and comments have skewered him as a “liberal,” he said. In the late afternoon, a UPS manager arrived with flowers, a $50 Kohl’s gift card and UPS tchotchkes.

“It’s been painful and it’s been interesting,” Berman said.

With Mark Morales