Garcia-Muro had also been hit by a bullet in the chest in what police dubbed a "skip round", after one of the bullets bounced off the pavement.
The sheriff's office released details of the incident in a statement and at a news conference, but did not identify the teen victim. His name was withheld pending family notification.
After the male pit bull first bit the deputy, Garcia-Muro restrained the dog behind the apartment complex that is also home to his mother, his aunt, and a neighbor who owns the dog.
Garcia was able to tie up the dog but it broke free and attacked again.
The dog ran to a carport around the back of the apartment complex.
Deputies immediately rendered medical support to the boy before paramedics arrived. As he jumped on the dog, he was struck in the chest with a bullet.
The injured teenager was shifted to Antelope Valley Hospital where he was pronounced dead later on.
The dog was also struck and taken for treatment by animal control.
The shooting was reported at 3:47 a.m.in the 38500 block of 10th Street East. It is unclear how many deputies were at the scene, and which deputies fired at the animal.
Bergner called the shooting an "extremely, extremely unfortunate incident".
"Our initial impression was [the deputies] didn't even see the individual coming around from the side of the building", Bergner was quoted as saying by the Los Angeles Times.
Robinson, whose daughter lives in the apartment complex near where the shooting happened, told KTLA she never witnessed the dog being aggressive. "They are good kids". The dog will likely be euthanized, according to the sheriff's department. She disputed authorities' claim that her dog attacked them. "That's not his personality".
The soon-to-be senior had recently transferred to R. Rex Parris High School "to get his credits up so he could graduate high school", Genevie Escobar, Armando's ex-girlfriend and one of his best friends, told BuzzFeed News. "He said he was done with his past life".