The teen had been burglarizing a car just before an officer shot him, police said in a statement.
Immediately following the shooting at about 2:30 p.m. near 48th Street and Baseline Road, one of the many police vehicles responding to the scene crashed into a car at University Drive and Rural Road, injuring as many as four people.
An officer initially responded to an alley at 4500 East Fair Lane in Tempe on Tuesday after someone reported a suspicious vehicle, according to the statement by Tempe police. The suspect fled the vehicle holding a handgun, and the officer gave chase, police said.
"During the chase, the officer perceived a threat and fired his service weapon striking the suspect," the statement says.
Officers found the teen near one end of the alley, performed CPR, and called paramedics. The boy was pronounced dead at a nearby hospital.
The boy's weapons was found to be a replica 1911 model Airsoft gun. It was apparently among the items the boy had swiped from the car.
Tempe police said a "thorough investigation" will be conducted with the Maricopa County Attorney's Office.
Meanwhile, the crash of the police SUV sent the officer driving it and two other drivers to a hospital. One car rolled, hitting a pedestrian. Two other people had minor injuries.
Police didn't immediately return a request for comment about the incidents from Phoenix New Times.
"Challenging day for our @TempePolice men and women today," Tempe police tweeted on Tuesday evening. "Thank you for the outpouring of support and concern. #Blessed to serve."