The 15-year-old who crashed a small plane into a skyscraper wrote a note expressing sympathy for Usama bin Laden and support for the Sept. 11 terrorist attacks, police said Sunday.

The short, handwritten note found in Charles Bishop's pocket said he acted alone, Tampa Police Chief Bennie Holder said. The high school freshman had no apparent terrorist ties, Holder said.

"Bishop can best be described as a young man who had very few friends and was very much a loner," Holder said. "From his actions we can assume he was a very troubled young man."

Bishop made an unauthorized takeoff in the Cessna 172R from a St. Petersburg airport, and began a flight that briefly included airspace over MacDill Air Force Base. Ignoring signals to land from a Coast Guard helicopter, he crashed into the 28th floor of the 42-story Bank of America building.

Bishop was the only fatality.

Holder said there is no indication Bishop specifically targeted the building or "had any intention of harming anyone else."

The note, a few paragraphs handwritten on plain white paper, was not addressed to anyone specifically, said police spokeswoman Katie Hughes. In the note he did not mention his family in it, nor did he say goodbye to anyone, she said, although authorities interpret it as a suicide note.

Investigators on Sunday interviewed the boy's family and said they would search his personal computer for evidence.

Bishop, of Palm Harbor, was told to check the plane's equipment before the start of a flying lesson Saturday, police said. He took off without waiting for an instructor who was supposed to accompany him.

A Coast Guard helicopter crew motioned for the boy to land but couldn't get a response, and a pair of military jets scrambled to intercept the small plane arrived after the crash.

Fire department officials said damage to the building was limited to the office where the plane hit and small areas of adjoining floors. Most of the building was expected to be open Monday, though there was concern about chunks of the facade falling to the sidewalk below.

Images of the plane blasting a hole in the side of a skyscraper were chilling reminders of the World Trade Center attacks. Until it was pulled in early Sunday, the plane's tail had dangled from the 28th floor of the building.

In Palm Harbor, police unrolled yellow crime scene tape Sunday outside the apartment complex where Bishop lived with his mother, while detectives and FBI agents interviewed family members.

Julia Bishop, the boy's mother, told a camera crew to "get out" when they attempted to film her as she opened her door for investigators.

Bishop's grandmother had taken him to the National Aviation Academy flight school at St. Petersburg-Clearwater International Airport for a 5 p.m. flying lesson on Saturday, authorities said.

National Transportation Safety Board Investigator Butch Wilson said the plane was airborne for just nine to 12 minutes, at one point flying through MacDill Air Force Base's airspace.

MacDill is home to Central Command, which is directing the war in Afghanistan.

Air Force Lt. Col. Rich McClain said the base was notified of the approaching aircraft when it was about three miles away from the base's airspace. One minute later, the plane entered MacDill's airspace and descended slightly. It left a minute later.

McClain said the plane made no threatening moves while nearing MacDill.

A Coast Guard helicopter caught up to Bishop over Tampa after he had traveled about 20 miles, and the crew signaled for him to land. Pilots said he ignored them, then crashed the plane into the building.

As a precaution, two F-15 fighter jets were scrambled from Homestead Air Reserve Base, 200 miles away, but they arrived after the crash, said Capt. Kirstin Reimann at the North American Aerospace Defense Command.

Only a few people were in the building at the time of the crash. None were injured.

The flight school canceled its regular operations Sunday. Employees reached at home said they had been instructed to refer questions to the school's attorney, Michael Cronin, who did not return calls for comment Sunday.

Investigators said it did not appear the any regulations were violated in leaving Bishop alone with the plane and its keys.

Police said the boy had no criminal record, no history of psychological problems and had not threatened suicide before. Investigators also said there's no indication Bishop used illegal drugs.

Derek Perryman, a classmate of Bishop's at East Lake High School in Palm Harbor, about 25 miles west of Tampa, said Bishop often talked about planes with a friend in their journalism class.

After the Sept. 11 terrorist attacks, he said, Bishop read a paper to the class. "It was real expressive about how he felt, how disappointed he was," Perryman told The Tampa Tribune.

Another classmate, Ross Stewart, 15, described Bishop as a "teacher's pet."

"I knew he was an honor student. He got straight A's," Stewart said. "He seemed to like his classes. He liked school. He was a happy kid. He was never really down about anything. He smiled a lot.

Bishop's algebra teacher described him as a bright, disciplined student who was well-liked by his classmates.

"I'm floored. Totally floored," said Rayette Bouldrick. "He always had a smile. He was always pleasant and respectful."

Neighbors said Bishop, who had moved from the Boston area a year earlier, kept to himself.

"He rode my bus to school. He sat in the front row. He always had sunglasses on for some reason," said David Ontiveros, 14. "He never talked to anybody."

Bev Pinkham, who lived near the Bishops in Norwell, Mass., said Bishop "was just an ordinary quiet kid."

"One day he came over and said my flower gardens were beautiful," she said. "Other than that, he was very quiet."

Michael Cronin, an attorney for the National Aviation Academy, said Bishop had been taking flying lessons since March 2001 and had logged about six hours of flight time.

He said the boy often cleaned planes in exchange for flight time and was very familiar with operations at the school. Cronin said students do preflight equipment checks on their own, then have their accuracy verified by an instructor. Bishop was a year shy of being able to fly alone and two years too young to earn a pilot's license.

President Bush was briefed on the incident and the White House officials had been in touch with Homeland Security Director Tom Ridge and the Federal Aviation Administration, said White House spokesman Scott McClellan. Two other small planes had crashed Saturday, one on a Colorado hillside near Boulder, and another in a vacant field near Los Angeles.