WESTON, Mass. – A pregnant real estate agent from Maine who was attacked by a dog when she arrived to show a house was released from the hospital Tuesday after undergoing surgery for her injuries.

Lisa Helfant, 42, of Spruce Head, Maine, an agent with Coldwell Banker Hunneman of Wayland, was attacked by a 60-pound dog when she arrived with her 2-year-old son to show a farmhouse Monday.

The house owner’s dog, named Tyson, attacked Helfant after she stepped from her car with her son, said Raymond Powell, 47, a tenant at the house, who witnessed the attack and eventually pulled the dog off.

Helfant frantically circled in an attempt to keep her body between her son and the dog, Powell said. Helfant fell onto her side, clutching her child to her chest as the dog locked its jaws on her side, he said.

Powell said he punched and kicked the dog several times before it finally released the woman.

“I must have hit it four or five times, but it wouldn’t let go,” he said. Powell was bitten on the wrist during the attack.

Police said the dog was a pit bull, but the owner, David P. Connolly, said it’s a mixed-breed Staffordshire terrier.

Helfant was discharged Tuesday from Newton-Wellesley Hospital in Newton after undergoing surgery, hospital spokesman Brian O’Dea said. A hospital spokeswoman said Helfant’s son suffered only scratches.

The dog was taken to the Natick Animal Hospital, where it will be tested for rabies, police said.

According to Connolly, Helfant had agreed to call the house before she came over so the dog could be put inside, but she never called.

“I’m devastated,” Connolly said. “I feel awful for the lady. I can’t understand why it happened.”

The district attorney’s office declined to file charges because the dog had no history of aggressive behavior, said Weston police Lt. Steve Shaw.