For decades, the Seabrook home had been a centrally located hangout spot for the family, and one of its newest members needed to get acquainted.
They were on the deck overlooking the beach around noon when they heard shouts from the water, he told the Washington Post: "Somebody help us!"
Six people wading in waist-deep water had got caught up in a riptide. In a flash, they were sucked out to sea, 100m offshore, just specks among the high waves.
There is no lifeguard at that section of beach. Tomaszewski's mother called emergency services, but there was no telling how long it would take the town's first responders to arrive. The people in the water didn't have that long.
So Tomaszewski and his father grabbed a paddleboard and a small surfboard and raced to the water's edge. On the beach, Tomaszewski, 29, stripped down to his khaki shorts and pleaded with his dad to stay out of the water. The older man had a knee injury, which would only hamper rescue efforts and put his own life in danger.
Tomaszewski persuaded his father to stay put, then grabbed the paddleboard, got on his knees and "paddled as hard as I could to get there as fast as possible."
Three of the people in the water had managed to latch onto a floating object and were making their way to shore. "They seemed headed in the right direction," Tomaszewski said. He kept paddling.
The remaining three were in more danger - a married man and woman and an unconscious man.
Sizing up the situation, Tomaszewski knew the paddleboard he was on was everyone's best chance to get back alive.
"They looked exhausted," Tomaszewski said of the couple. "And they were in shock."
Tomaszewski played Division One basketball at Syracuse, and he had grown up around the water, including countless summer days spent on that stretch of beach. More than anything, he said, that gave him a good understanding of the danger they all faced.
Together, he and the married couple tried to get the unconscious man's torso onto the board, but the water was relentless. A large wave smashed into the group, knocking the unconscious man off the board.
"I was just trying to do everything in my power to save and help" the man, Tomaszewski said. "Then we get bashed with that wave, and I knew there were more coming."
He extended the board to the couple.
"I looked at them and said, 'If you want to survive, you need to grab this board,' " he said.
He helped the woman and the man onto the paddleboard, then used his 6-foot-8 frame and a passing wave to help launch the couple toward the shore. The wave did the work. Quickly, the couple was closer to safety.
Tomaszewski watched, bobbing in the water.
"The toughest decision I ever had to make was trying to send those people in," he said. "I really had to think about did I have enough energy to get back myself."
When he turned around, the unconscious man was gone.
"I couldn't see him," Tomaszewski said. "Another wave must have taken him . . . That's when I came to the realisation that now I'm in the middle of the water with no board."
On shore, the people watching from the beach were just dots. His wife and daughter were surely among them, he thought to himself.
They had seen him go into the water on a paddleboard, then saw that same paddleboard come back "with two people on it, and I wasn't one of them," he said.
He gave one last look, then turned and swam to shore.
Later that day, he was a sentence in a New Hampshire State Police news release: "A Good Samaritan was able to help the six swimmers to shore."
Police announced that two of the swimmers were unconscious when they came to shore. A woman died, according to Boston CBS affiliate WBZ-TV. And Tomaszewski didn't need a news release to tell him what happened to the man knocked off his paddleboard. A lifeguard found his body on the beach, a few hundred metres south of where he disappeared.
The death still haunts him, although, replaying the moment in his mind, he doesn't think he had another choice that would have saved him.
His emotions were buoyed somewhat after he met the people he had sent to shore on his paddleboard. They were friends of his parents, and parents themselves.
"I found out later that he has three daughters. He's a father. And I'm a new father," Tomaszewski said. "It's amazing to help him get back to his children. It was amazing to tuck Chloe in that night."
