Fifty years ago today, Charles Whitman, a 25-year-old engineering student and former Marine armed with a small arsenal of weapons, killed 13 people and wounded over 30 more during a shooting rampage atop the University of Texas Tower in Austin. The episode casts a long and complicated shadow. It is considered by some to have marked the beginning of the era of mass shootings; for others, the armed civilians who engaged Whitman that day suggest one way to limit the scope of such attacks.

As survivors and mourners gather to mark the anniversary on Monday, a campus-carry law that allows firearms in university buildings in Texas will also go into effect.