WASHINGTON — Musician Seth Horvitz is used to tickling the ivories, not squeezing a trigger.

So when a UPS delivery worker dropped off a military-grade semiautomatic rifle instead of the flat-screen TV he had ordered from an Amazon.com third-party seller, he didn't dare touch it at first.

"When I first identified it as a rifle, as a serious weapon, I was just shocked and confused," Horvitz said Thursday. "I didn't ever really imagine this kind of mix-up could happen."

Horvitz, 38, wasn't immediately alarmed by the long rectangular box a UPS delivery worker had dropped off in the hallway of his apartment building Tuesday. While he knew it wasn't the right shape or size to hold the 39-inch TV he had ordered, he said he thought maybe it contained a television stand or accessories and that the actual monitor would be delivered later.

But when he opened the box, he found a fully assembled rifle in a plastic bag, surrounded by foam.

Horvitz said he called the police, who confiscated the gun and told him it was illegal in the District of Columbia to handle such a weapon.

He also contacted Amazon, UPS, the seller and his credit card company. At first, he said, "No one claimed any responsibility."

The seller of the television has refunded Horvitz and is now involved in filing a claim with UPS and reporting the package as lost, Horvitz said.

Horvitz said he believes the mix-up to be a shipping error, especially since there were multiple UPS labels on the box and an invoice inside indicating that the company, GunBuyer.com, intended for it to be delivered to a gun store in Duncansville, Pa.

"I got my money back and I'm happy to be absolved of the situation at this point," he said.

No one from Amazon or UPS immediately returned emails seeking comment.