The perpetrator of Wednesday’s horrific school shooting in Parkland, Fla., purchased his military-style assault weapon legally. So did the man who shot more than 400 people in Las Vegas in October. So did the man who gunned down 49 people at Orlando’s Pulse nightclub in 2016. So did the man who gunned down 26 worshipers at a church in Texas in November.

Easy-to-obtain assault weapons, once banned under U.S. law, are a common thread connecting many of the deadliest mass shootings that have occurred in the past few years. Many gun violence experts believe that it’s time to bring back the federal assault weapons ban — or at least something like it.

“You would see drastic reductions in what I call gun massacres” with the return of the 1994 federal assault weapons ban, said Louis Klarevas of the University of Massachusetts at Boston.