Lane's grandfather believes the gun is the same, "because the gun was there the day before, in the barn," said Henderson, 74, who says he's been friends with the boy's family for nearly 50 years.
A law enforcement official familiar with the investigation said the gun used in the shooting, a Ruger .22-caliber Mark III target pistol, was bought legally in August 2010 from a gun shop in Mentor, Ohio.
The official, who spoke to The Associated Press on the condition of anonymity because of the ongoing investigation, said Lane told authorities he stole gun from his uncle. It wasn't clear Wednesday whether the gun might have been the same one missing from the grandfather's barn.
The grandparents feel terrible about what happened and have no explanation for the teen's alleged role in the shootings, Henderson said.
Lane came from a broken family but seemed to heal over time, said Henderson, who added that the boy began living with his grandparents off and on several years ago. He didn't know where he stayed when he wasn't with them.
"T.J. was a very fine person," Henderson said. "Nice-looking man, very friendly, spoke to you, carried a conversation with you."
Another neighbor on Wednesday described T.J. Lane as a normal boy who excelled in school and played outside often with his sister, building snow hills and skateboarding, a family friend said Wednesday.
Steve Sawczak said he never would have allowed his own grandchildren to play nearby if he thought anything was wrong with suspect T.J. Lane.
"We're all absolutely stunned," Sawczak said. "He's an average kind of kid."
Sawczak, 58, a pastor who has worked with troubled children, said he never saw hints of what was coming. A next-door neighbor of Lane's grandparents for almost 25 years, he said the couple, who have custody of the teen, gave Lane a healthy place to live. They often took them to school events.
"They are in shock," Sawczak said. "They are absolutely devastated."
At Chardon High, the faculty parking lot was jammed Wednesday as teachers returned to the school for the first time since Monday's shooting, with grief counselors on hand if needed. Parents and students are encouraged to return to the school Thursday, and classes resume Friday.
Hundreds of residents turned out for a vigil Tuesday evening at St. Mary Catholic Church to pray and hear Scripture readings, while overhead banners from a rival high school contained signatures from other students showing their support.
Lane, 17, admitted taking a pistol and a knife to the 1,100-student Chardon High and firing 10 shots at a group of students sitting at a cafeteria table, prosecutor David Joyce said.
Lane, a thin young man described by other students as extremely quiet, appeared briefly in juvenile court Tuesday. He spoke little, and a judge ordered him held for at least 15 days.
Prosecutors have until Thursday to bring charges and are expected to ask that Lane be tried as an adult. He will probably be charged with three counts of aggravated murder and other offenses, Joyce said.
Joyce described suspect Lane as "someone who's not well" and said the teen didn't know the victims but chose them randomly.
Killed were Demetrius Hewlin, 16, Russell King Jr., 17, and Daniel Parmertor, 16.
An 18-year-old girl who was hurt in the shootings was released from the hospital Tuesday and was home with family. The girl's family declined to comment Wednesday. The second injured teen remained in serious condition at a suburban Cleveland hospital.
Both sides in the legal case are under a gag order imposed by the judge at the prosecutor's request. The judge also barred media outlets from taking photos of the faces of the suspect and some of his relatives.
The Associated Press transmitted photos and video of Lane that were shot before the hearing. The AP and at least one other media outlet, The Plain Dealer of Cleveland, plan to challenge the judge's order Wednesday.
Sanner reported from Willoughby, Ohio. Associated Press writers Pete Yost in Washington and Andrew Welsh-Huggins in Columbus contributed to this report.