“They had two backpacks. I reached out to help them put them in the trunk, and they wanted to put them in themselves,” said Duggan.

The two men were adamant about handling those backpacks themselves.

During the ride, Duggan and his passengers talked about a lot of different things. The Boston cab driver asked them if they were from Saudi Arabia. They said they were from Chechnya.

As the cab approached its destination, Duggan pointed to an area over the bridge, and told them that the Boston Marathon would be held there the next day. If they hadn’t seen it, said the friendly cabbie, it might be a good experience.

“And the little brother said, ‘Oh, Boston Marathon?’,” said Duggin. “And then the older brother got real aggressive.”

The younger passenger began reassuring Duggan, telling him the fight was just between him and his brother. He told Duggan to pull over.