CAMPBELL — Like millions of people, Paul Bondonno searched in vain for an explanation for the deadly shooting at Sandy Hook Elementary School. But when early reports noted the gunman had Asperger’s syndrome, the 34-year-old bolted into hyper-driven self-defense, and he hasn’t stopped since.

“We don’t want Adam Lanza to be our poster boy,” Bondonno said at the Coffee Society in Campbell.

The cafe is usually busy on weekends, but a pelting rain Sunday morning kept the crowd and noise down, a perfect setting for separating the facts of a mysterious disorder from the debate over guns, massacres and mental illness. A 13-year-old girl with Asperger’s, Puja Uppalapati, and her father, joined the conversation as well.

“It irritated me,” Puja said about the initial Lanza-Asperger’s connection. “I was like, why are you saying this? Is this what people will think of us?”

Medical records have not confirmed it, but the possibility that Lanza, the 20-year-old gunman, had Asperger’s has got people such as Puja and Bondonno worried that any association with Lanza, true or false, will create a runaway stereotype of them as murderous madmen waiting to explode.

Considered a form of high-functioning autism, Asperger’s is a neurological disorder generally characterized by difficulties with social interaction and communication with others.

Children who have autism may have more severe tantrums and meltdowns than other youths, but the disorder is not typically linked to violence, said Mohan Krishnan, a clinical neuropsychologist who works with children and adults who have Asperger’s at Hope Network Behavioral Health Services in Grand Rapids, Mich.

“In adulthood, planned acts of violence are not associated with people with Asperger’s,” Krishnan said.

People who have Asperger’s “have normal intelligence or better,” and some become university professors or work in other professional jobs, often in technical fields, Krishnan said.

But they sometimes struggle to communicate, may not understand slang or jokes, and may have difficulty in social situations, he added. Some develop an unusual preoccupation with a particular topic, such as train schedules or football helmet designs.

Asperger’s usually goes undiagnosed until a child enters school. That was the case with Puja.

Especially good in math and above average in other subjects, her grades began to fall in the fifth and sixth grades, and she received bad marks for behavior.

“The teachers kept saying I had to respect others more and stop interrupting them,” she said.

According to her father, Siva Uppalapati, a microchip designer, it took a long time for school psychologists to confirm his daughter’s condition. Only then did the school provide special assistance. Today, Puja sees a speech and language therapist twice a week at school. She gets unlimited time for completing tests because her writing is slower than average. Her grades have improved but the bright, precocious girl wants better.

“I’m good at logic and strategic thinking,” she said. “It irks me that I’m getting B’s and B-pluses when I should be getting all A’s.”

She also receives instruction in social skills from Bondonno, who teaches the subject for the Asperger Society.

Where Puja’s disorder was caught early, Bondonna had to run the gantlet before he was diagnosed at age 20. He was bullied relentlessly in school, he said, and misdiagnosed four times, once as a potentially violent youth who should be institutionalized. But his mother refused to believe he had a psychological disorder. Finally, medical researchers determined he had Asperger’s, a neurological condition.

“It took me years to come to terms with all the mislabeling,” Bondonno said. Today, he’s frank, even humorous, about the challenges of living with Asperger’s.

“I’m hyperactive,” he said, “and sometimes I don’t know when to stop talking, or when I’ve made my point too many times, but I’m getting better about that.”

It’s that sort of social difficulty, Bondonno fears, that people will associate with Lanza and violence. That could lead to a range of rejection of Asperger’s sufferers, from schoolyard bullying to discrimination in employment and social shunning. Those prospects, Bondonno said, could drive individuals with Asperger’s into the closet to avoid the stigma and away from treatment.

Several of Lanza’s classmates described him as a loner who shied away from others, but Bondonno said that’s not necessarily a diagnosable trait of the condition. Krishnan agrees.

“Most of them have close connections, particularly to family,” Krishnan said. “A lot of them, if not most of them, desire friendships.”

Even if Lanza had Asperger’s, experts say he may have had mental illnesses that led him to the violence.

Meanwhile, Bondonno has been running a nonstop, one-man crusade to explain Asperger’s to a nation looking for answers. He has a new website in the works and is connecting with Asperger’s networks across the country.

“This is our breakthrough moment, and we can’t let Lanza speak for us. We have to speak up for ourselves,” Bondonno said.

Staff writer Sandy Kleffman contributed to this story. Contact Joe Rodriguez at 408-998-8079. Follow him on Twitter.com/JoeRodMercury.