Randy Sterne got chills Thursday as he watched hundreds of balloons sail into a bright, sunny sky at the start of a 3.2-mile run to honor 32 people killed by a student gunman at Virginia Tech two years ago.

Sterne walked the race course with his son, Kevin, who was injured in the shooting, the worst mass slaying in modern U.S. history. He noted the difference between this year and last, when events to mark the first anniversary started with a chapel service for the families.

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"It's a different kind of flavor on the day," Sterne said. "It's more uplifting."

Some 4,300 people, including several students hurt in the shootings and their families, joined the race around the main section of campus. It started with the release of 32 white balloons in memory of those killed by Seung-Hui Cho, who also took his own life. Runners then released balloons of maroon and orange, the school colors.

Later in the day, more than 2,000 people gathered for a more somber event to remember the accomplishments of the 27 students and five faculty members killed.

"While the tragedy of April 16, 2007, touched us all, we know that 32 families continue to confront the deepest of all losses — the loss of a loved one, the loss of a life well-lived, and the loss of a bright and promising future," said Virginia Tech President Charles Steger.

Five students injured in the shootings participated in the memorial service. One, Colin Goddard, read an old Celtic prayer that said in part: "Be gentle as you walk with grief."

Earlier in the day, students hurt in the shootings and their families were the core of the group of runners in the memorial race. Most of the 12 still on campus participated, said Debbie Day, head of the school's Office of Recovery and Support.

Katelyn Carney, one of the injured, graduated in December but came back for the anniversary.

"This is where it matters," she said as she got ready to run with a friend. Her mother was part of the group walking.

Injured student Derek O'Dell said the race was bittersweet.

"It's difficult, but I think it's important," he said.

The mood was upbeat as students crowded around a table to sign a message banner before the race.

"Not a day goes by that we don't think about it," said Fred Cook, an engineering student who injured an ankle when he jumped from a second-floor classroom window to escape the gunfire. "This increased sense of awareness by everyone certainly makes it more acute for us."

Events also included an open house in a new peace center that occupies a refurbished classroom wing where most students were killed. The final event was a candlelight vigil at dusk.

Classes had already been canceled, but the response to the "3.2 for 32" race was so great that the school also delayed opening offices until midmorning to avoid traffic jams.

About 100 relatives of victims and injured students returned for the memorial ceremonies — a few more than last year, Day said. Many still find it too painful to return, said Joseph Samaha, whose daughter Reema Samaha died.

Suzanne Grimes, Kevin Sterne's mother, said memories came flooding back when she arrived Wednesday at the hotel where she spent 28 days while he was hospitalized.

While most families accepted an $11 million state settlement and agreed not to file suit, some remain critical of school officials' actions the day of the shootings. Samaha said he wanted to come to campus not only for the anniversary events, but also "to work on bridge-building."