Justin Ireland says he always wondered how his dog Thor, a beefy 3½-year-old pit bull-boxer mix, would respond if he got into an altercation.

Now he knows.

Ireland, 21, was working at Holly’s Gas, the hot pink gas station on Route 1 in Saco, when a man walked up to the door of the office at 3:25 p.m. Tuesday and asked to use his phone. A mask-like covering partially obscured the man’s face. Ireland figured he was just bundled up against the cold.

Thor was excited to have a visitor, so Ireland used a knee to keep the dog back as he opened the door, so Thor wouldn’t run outside.

When Ireland refused the man’s request, because he doesn’t let anybody use his phone, the man pulled out a gun, shoved Ireland and demanded money.

Ireland was startled and scared at first. But with the small gun pointed right at him, Ireland could tell that the diameter of the barrel was too small to accommodate even a .22-caliber bullet, leading him to conclude it was a BB gun.

“I went from nervous to pissed off,” he said. “I said, ‘I can’t believe you have the (gall) to pull a BB gun on me,'” Ireland said.

The would-be robber yelled back that it was real and moved to shove Ireland again. Before Ireland realized what was happening, Thor had leapt past his still-outstretched knee and lunged at the gunman.

“Once he came at me the second time, that’s when Thor went after him,” he said.

The man turned and fled. Ireland pulled Thor back inside, then chased the man. He lost his footing on the snow and the man made it to a light blue, newer model Chevrolet Silverado extended cab pickup truck, which had been parked around the corner from the station on Flag Pond Road. The man drove away.

Later, police reviewed security tape frame by frame and saw that Thor had landed a couple of good chomps, biting one side of the man’s face and then the other. Ireland said he doesn’t believe that Thor’s bite, as powerful as it is, broke the skin beneath the mask.

The robber remains at large and police are still looking for him. He was last seen wearing a navy blue sweatshirt with the word “GAP” written across the front, black pants, gray and black gloves, a winter hat and a dark green mask with orange liner covering the bottom of his face.

“He was tiny – the same height as me but skinnier,” said Ireland, who is 5 feet 9 inches and 315 pounds.

Saco police ask that anyone with information call them at 282-8216.

Ireland said he got Thor when the dog was 11 months old from a woman in New Hampshire who was moving in with her sister and couldn’t keep him. The shelter where he was headed would have euthanized him because he is part pit bull, Ireland said.

As news of Thor’s intervention spread late Tuesday, the accolades started to come in. More exciting for him, someome brought him a big bag of dog treats, Ireland said.

“After work, I went out and bought him one of those big, $20 bones,” Ireland said.