ANOTHER U.S. mass shooting, this time at an airport in Florida. This time, five people were killed and six others injured, some grievously. This time, those senselessly gunned down were picking up their luggage before going to board cruise ships for eagerly anticipated vacations. This time, once again, the all-too-easy availability of firearms allowed a gun to get into the hands of the wrong person.

Esteban Santiago, a 26-year-old Iraq War veteran who has been described by family members and authorities as having mental-health issues, made his first court appearance Monday on federal charges stemming from Friday’s shooting rampage in the baggage-claim area of the Fort Lauderdale airport. Investigation is continuing as authorities try to sort out what prompted him to travel, a semiautomatic legally checked in his luggage, from Alaska to Florida, and whether terrorism was a motive.

Prior to Friday’s rampage, Mr. Santiago had shown signs of violence and what authorities characterized as “erratic behavior.” There had been frequent run-ins with law enforcement, allegations of domestic violence and a visit in November to the Anchorage FBI office in which he made disturbing remarks about his mind being controlled by a U.S. intelligence agency. Local authorities were contacted, and he was transported to a local mental-health facility for evaluation. A gun, the same one authorities say was used in the airport shooting, was taken for “safekeeping” but returned to him a month later because there was no legal justification to withhold it.

There is, of course, no way of knowing whether the attack could have been prevented. But there are obvious questions that need to be addressed. What kind of mental-health treatment was offered to Mr. Santiago? Was there a failure of the system? Could the family have taken action? Was the FBI response adequate? And, given this is the third instance in which an alleged mass killer had previously come to the attention of the agency, is a review of their threat assessments in order?

We also can’t help wondering what the outcome might have been had Mr. Santiago’s family and law enforcement authorities had the benefit of laws that allow the removal of guns from people who have been deemed to be a high risk. Four states — California, Connecticut, Indiana and, most recently, Washington — allow law enforcement and family members to petition a court for a protective order to temporarily suspend a person’s access to guns if the person poses a danger to himself or others. Studies show promising results, particularly in preventing suicides, and there have been no reports of misuse. It is a common-sense measure that other states should adopt.

Unfortunately, there seems to be a push in statehouses across the country to go in the opposite direction by loosening, not tightening, what controls do exist. Florida, the scene of two recent mass shootings, is considering changes that would eliminate gun-free zones in schools, colleges — and, yes, airports. As if more guns would have helped Friday when five people were killed in some 80 seconds.