NEWTOWN, Conn. — The man suspected of gunning down more than two dozen people Friday in a small town in Connecticut is the son of a teacher at the elementary school where the killings occurred, and his mother is presumed to be among the dead, police said.

Adam Lanza apparently drove to his mother’s school carrying three weapons — two handguns and a .223-caliber rifle — and carried out the massacre. Law enforcement officials were trying to learn as much as possible about the 20-year-old and questioning his older brother, who is not believed to have any involvement in the rampage.

So far, authorities have not spoken publicly of any possible motive.

Several neighbors of the Lanza family in Sandy Hook, a community about 60 miles northeast of New York City, said they knew little about them.

A grandmother of the suspect — who is also the mother of teacher believed killed at Sandy Hook Elementary School — was too distraught to speak when reached by phone at her home in Brooksville, Fla.

“I just don’t know, and I can’t make a comment right now,” Dorothy Champion, 78, said in a shaky voice as she started to cry. She said she hadn’t heard anything official about her daughter and grandsons. She declined to comment further and hung up.

Adam Lanza’s older brother, 24-year-old Ryan Lanza of Hoboken, N.J., was being questioned, a law enforcement official said, speaking on condition of anonymity because he was not authorized to speak on the record about the unfolding investigation.

Sandeep Kapur, who lives two doors down from the Lanza family in Newtown, said he did not know them and was unaware of any disturbances at the Lanza house in the three years that he and his family have been in the neighborhood.

He described the area as a subdivision of well-tended, 15-year-old homes on lots of an acre or more, where many people work at companies like General Electric, Pepsi and IBM. Some are doctors, and his next-door neighbor is a bank CEO, said Kapur, a project manager at an information technology firm.

“The neighborhood’s great. We have young kids, and they have lots of friends,” he said. “If you drive past this neighborhood, it gives you a really warm feeling.”

Several local news clippings from recent years mention Adam Lanza’s name among high school honor roll students.