A mentally disturbed man reaches the top of a tall building that overlooks a large, busy open area.

He takes a military-grade weapon and guns down people on the ground below.

Police eventually storm into the room he converted into a sniper’s nest, but not before the shooter takes numerous innocent lives.

In short, this is what happened on October 1, 2017, in Las Vegas.

It is also what happened on August 1, 1966, in Austin, Texas.

On that summer day over 50 years ago, 25-year-old Charles Whitman rode an elevator 27 stories to the top of the clock tower on the downtown campus – his Marine sniper rifle in tow.

RELATED: Photographer tells story behind picture from Las Vegas shooting

Before opening fire on the crowd below, he murdered his wife and mother.

Whitman’s shooting spree lasted 96 minutes, during which he killed 14 people and wounded 31 others.

Police eventually reached the top of the tower, using deadly force to take Whitman out.

At the time, his massacre was the deadliest shooting in U.S. history. The incident also marked a notable point in the timeline of “mass shootings” as news events.

According to author and criminologist Grant Duwe, since the UT-Austin sniper attack, more than 150 mass shootings occurred in the U.S.

Duwe said he qualifies a mass shooting as an incident where four or more people are murdered in a public place, with no apparent criminal motive, such as a gang war or drug deal.

RELATED: Las Vegas shooter’s motives remain a mystery even after details emerge

“The UT-Austin shooting was the bellwether for the unprecedented rise in mass public shootings in the last half-century,” Duwe said in an interview.

Las Vegas (2017) is now added to this lineup, which also includes:

  • Austin, Texas (1966)
  • Littleton, Colorado (1999)
  • Blacksburg, Virgina (2007)
  • Sandy Hook, Connecticut (2012)
  • San Bernardino, California (2015)
  • Orlando, Florida (2016)

The list goes on.