DAVID GREENE, HOST:
All right, it's been more than a week now since that deadly shooting in Las Vegas. And investigators are still searching for some kind of motive. At a press conference yesterday, Las Vegas Sheriff Joseph Lombardo said understanding why this happened is absolutely their priority.
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JOSEPH LOMBARDO: As I've said from day one, we want to figure out why and we'd like to know the motive. That is our most important goal.
GREENE: NPR's Sarah McCammon has been reporting in Las Vegas. And she set out to understand why motive matters.
SARAH MCCAMMON, BYLINE: Markie Henderson is grateful that her brother and sister got out of the music festival alive last week.
MARKIE HENDERSON: So they were upfront. And, you know, they saw kind of everything happening. They got split up in between it. My brother actually went back into it looking for my sister.
MCCAMMON: They both made it out physically unharmed. But it's still really close to home. And Henderson says she wonders what could motivate someone to do this.
HENDERSON: But, yeah, I think, you know, for the ones' families that were affected, I would want to know what happened to my brother or sister if it was one of them, for sure.
MCCAMMON: Henderson came to the opening of a memorial garden honoring the victims in Las Vegas late last week. Volunteers worked together in the days after the shooting to plant 58 trees honoring the dead. Precy May Lawson came to bring some handmade ornaments honoring each victim to leave on a wall of remembrance at the park. She says the lack of answers takes a toll on the whole city.
PRECY MAY LAWSON: There's so many questions. And we don't know the answer. We don't know - and sometimes I'm just tired of, you know, asking the question that I don't have the answer. So I just leave it up to him.
MCCAMMON: With that, Lawson pointed to the sky, to God, she said. Investigators, meanwhile, are looking everywhere for answers, talking to anyone who might have known the shooter.
JOHN IANNARELLI: First and foremost is we want to prevent future attacks.
MCCAMMON: John Iannarelli is a retired FBI agent and terrorism expert. He says this is a tough case with no clear sign of a religious or political motivation.
IANNARELLI: We want to make sure that if there was something in particular that set this person off or caused them to change their thinking, that'll become an indicator in the future if somebody else engages in such behavior.
MCCAMMON: Iannarelli says sometimes exploring the motive can help investigators discover whether anyone else was involved. There's also a psychological need to know, both for survivors and the larger community. Priscilla Dass-Brailsford is a trauma psychologist and professor based in the Washington, D.C., area.
PRISCILLA DASS-BRAILSFORD: Oh, it comes up a lot because, you know, people just cannot believe that one human being would inflict this kind of violence and harm on another.
MCCAMMON: Dass-Brailsford has worked with trauma victims after both natural disasters and violent attacks. She says it can be especially hard for people coping with violence to find answers.
DASS-BRAILSFORD: So then we want to understand why the person did it. And then when the person is not even available to explain why, it just makes it harder. What survivors really need sometimes is to get closure.
MCCAMMON: Investigators say they're still hopeful they will find a motive if for no other reason than to help prevent yet another deadly attack. Sarah McCammon, NPR News, Las Vegas. Transcript provided by NPR, Copyright NPR.