A rifle used in the 1966 sniper rampage at the University of Texas that left 16 people dead and dozens more wounded is being sold in an online auction.

Bids are starting at $25,000 for a rifle Charles Whitman used to shoot from the top of a clock tower on the campus in Austin.

Donald Weiss of Dallas told The Associated Press in a telephone interview Thursday that he's helping the owner of the Remington 700 sell the weapon, which has changed ownership several times over the decades. Bids are being accepted on the website of Texas Gun Trader.

The rifle was listed in a probate court inventory in Travis County, according to a copy of the 1967 document shared with AP. The executor of Whitman's estate sold the weapon and six others recovered from Whitman's arsenal at the tower to a Wichita Falls gun dealer, according to Weiss.

"The deal in Texas is, no matter what's happened or how many people were shot, this is private property," Weiss said.

He declined to reveal the owner's identity.

Whitman, 25, was a Texas student and former Marine when he opened fire just before noon on Aug. 1, 1966.

Police who made their way to the tower's observation deck shot and killed Whitman after the sharp shooter spent more than an hour firing on people with terrifying accuracy — hitting people as far as 500 yards away. More than three decades later, a 17th death would be attributed to Whitman in 2001 when a Fort Worth man died of injuries from the shooting.

Authorities later determined Whitman also killed his wife and mother in the hours before he went to the tower.

Mary Jane Flowers' brother and aunt were killed in the tower shooting, and her mother was left a paraplegic. Flowers, who lives in West Memphis, Arkansas, was "shocked" to learn of the sale.

"I can't imagine who would want that or who would do that," she said in a telephone interview.

It was the deadliest shooting by a single gunman until 2007, when a student at Virginia Tech shot and killed 32 people and wounded 17 more.

"We're not capitalizing on the horrific part," Weiss said. "This is strictly for collectors, for its historic value."