Authorities said the suspect, Audrey Hale, was not on their radar before the attack.
Construction crews recently turned the low-slung Cable Center Shops, Boulevard food court and outdoor Fatburger eatery with slushie bar into piles of rubble.
Central Las Vegas may reach 70 on Tuesday, which would be just the fifth 70-degree or better high of the month.
The teen killed in a shooting in a hotel room just off the Las Vegas Strip was a student at Legacy High School in North Las Vegas and played football there.