“They’re all very positive and you almost stay in the moment with the events and then — you know why you’re here and you don’t want to be here,” Petit said as he choked back tears.

“So you just try to stay in the moment and stay positive because even though you feel like crying, you figure you don’t want to cry in front of 20,000 people at every event,” he added.

Lisa Gerrol, president of the Greater Connecticut Chapter of the National Multiple Sclerosis Society, who knew Petit’s wife and daughters, said she sees the diabetes doctor continuing his family’s efforts to help others.

“I think that his emphasis from the very beginning is that he wants to take the most horrible situation that could happen to anyone and turn it into something positive, something good,” she said.

About $350,000 has been raised for the MS society. Both Petit children had supported the society after their mother was diagnosed with the disease.

Gerrol said she’s never seen such an outpouring of support.

“It’s a huge amount of money. Raising $350,000 is no simple feat; it takes a lot of hard work and effort,” she said. “And I don’t believe it’s finished.”

In all, donors gave about $1 million to charity in the family’s name, including $600,000 to the Petit Family Foundation that will encourage young women to study science, help people suffering from chronic illness and assist those affected by violence. Some grants have already been awarded.

There are also funds honoring the late mother and her two daughters at schools where they worked and attended.

Petit, 51, has become involved in all aspects of fundraising events — from designing the medals given out to children at Sunday’s road race to helping to choose scholarship recipients for the MS Society.

“Billy’s always been strong,” said Bob Heslin, who organized the road race with his brother Gary. “He was our class president in 1974. He was a leader then and he’s a leader now. There’s not too many people who could do what he’s doing.”

Petit had the house where his family died torn down, although town records show he still owns the land. All that remains today are a few flower gardens growing in an empty lot and a large heart carved into what was once the lawn.

Petit moved in with his parents in nearby Plainville and sees a counselor, according to his mother-in-law, Marybelle Hawke.

“He still doesn’t know who he is and what every day’s purpose is,” Hawke said. “He still feels like he’s lost all his purpose for living.”

Dr. Earle J. Sittambalam, president of Grove Hill Medical Center in New Britain, said he sees Petit, his friend and colleague of 20 years, at monthly Hartford County Medical Association meetings and notices how he has changed since the crimes.