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

Some researchers think mass shootings are contagious. A few months after Whitman’s rampage, an 18-year-old man in Arizona named Robert Smith shot five people to death, saying in a note that he was inspired by Whitman. It is, Duwe writes in his book, “one of the clearest examples of the copycat or contagion effect.”

In the five decades since the UT Tower shooting, students have become some of the most prolific mass shooters. In 1999, Eric Harris and Dylan Klebold attacked classmates at Columbine High School, killing 13 and wounding 23. In 2007, Seung-Hui Cho fatally shot 32 people at Virginia Tech University. Last year, Chris Harper Mercer killed nine at Umpqua Community College.

The national campus-carry movement took shape after Virginia Tech, with the formation of a group called Students for Concealed Carry. The group argues that so-called good guys with guns can save lives by confronting gunmen and taking them down — rhetoric that was echoed by National Rifle Association President Wayne LaPierre after 20 first-graders were killed at Sandy Hook Elementary School in 2012.

“Campus police simply cannot be dispatched in time to stop a madman from taking innocent lives,” Students for Concealed Carry says on its website. “Only the people at the scene when the shooting starts — the potential victims — have the potential to stop such a shooting rampage before it turns into a bloodbath.”

In Texas, concealed-carry legislation signed by then-Gov. George W. Bush in 1995 did not prohibit permit holders from carrying weapons on college campuses, but taking guns inside buildings was illegal. Pro-gun legislators had been trying to change that for more than a decade.

They failed in 2009, 2011 and 2013 — the Texas legislature convenes every other year — amid fierce opposition from university presidents, but tried again last year.

Campus carry passed, though private universities were allowed to opt out, and each public school could decide where guns will be allowed.

At UT, guns will be allowed in classrooms and in common areas of dorms but not dorm rooms. Guns were already prohibited at sporting events. Professors with their own offices can ban students from bringing guns to meetings, but those who share offices cannot.

[Guns go to college: Everything you need to know about campus carry]

A group of UT professors has filed a lawsuit against the state, arguing the new law violates their academic freedom. They contend they will have to censor themselves on controversial topics such as religion and politics so they do not get shot. Students opposed to the law have similar concerns. In studying the issue, UT officials contacted schools in states where campus carry has become legal but found little evidence of violence as a result, according to a report issued last year.

“As a professor, I understand the deep concerns raised by so many,” Fenves wrote in a letter to the university community. “However, as president, I have an obligation to uphold the law.”