A police dog searching for a handgun in a Massachusetts snowbank early Saturday accidentally pulled the trigger with his paw, discharging the weapon into a nearby house, authorities said.

Fortunately, no one was injured.

"I've been policing for 43 years and I've never seen or heard anything like this," Lawrence Police Chief John Romero told NBC News. "It's amazing."

Romero said Jeffrey Hart, a Lawrence police officer on patrol, heard three loud gunshots shortly after 2 a.m. Saturday. When Hart went to investigate, he saw a sedan barreling down the road at a high speed.

As he followed the car, he saw one of the passengers get out of the car and a bury a pistol in a mound of snow on the road's shoulder, Romero said.

Hart eventually pulled over the grey Honda Accord and found a 9mm shell casing inside -- and that's when officers from the Essex County Sheriff's Office were brought in to help locate the missing weapon. Officials with the sheriff's K-9 unit arrived at the scene with their 3-year-old black German Shepherd, Ivan, in tow. 

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As Ivan started digging in the snowbank for the buried pistol, he accidentally pulled the weapon's trigger, firing one shot into a nearby residence, Romero said.

"The officers were sure the dog was hit," Romero said. "But luckily, he wasn't. He was just startled."

Police were unable to locate the bullet, but they woke up the residents of the house to confirm no one was wounded.

The three men Hart found in the vehicle — Jose Calderon, 28; Alexander Gonzalez, 21; and Jorge Henriquez, 26 — were taken into police custody and charged with unlawful possession of a firearm and ammunition, receiving a firearm with a defaced serial number, and receiving stolen property, according to authorities.