Lanza, 20, killed his mother and then went on a shooting spree at Sandy Hook Elementary School on Friday. Twenty children and six adults died. He then fatally shot himself.
"[My family] didn't want me to go to the press but I thought someone from the Lanza family should be represented," Marsha Lanza said. "We feel it just as much as those families of the 20 lost angels."
Marsha Lanza, lives in Crystal Lake. She said she hadn't seen her nephew, Adam, since he was 3 years old and her family has very little interaction with the Lanzas in Connecticut.
"It has tarnished the name. We are related, but did not have anything to do with it," Marsha Lanza said. "My three younger boys did not know their cousins."
Lanza said she called her son's school to let them know about the connection.
"If there are any issues or problems my kids are smart enough, hopefully strong enough to turnaround and walk away," Marsha Lanza said.
Marsha Lanza said she has not heard from Adam Lanza's father, Peter.
"Nothing. I'm shocked. We're worried," Marsha Lanza said.