In the aftermath, many have questioned why the deputy who fired his handgun did not try to disable Lopez by aiming for his legs or arms.
The most effective way to stop a threat is to shoot a suspect in the body, or "center mass," several experts said. A shot to the leg may not neutralize a suspect with a gun, they say, and shooting the gun out of a suspect's hand is the stuff of movies.
"Police officers are taught to shoot to stop a deadly threat," said Richard Lichten, a former law enforcement officer in Southern California and use-of-force expert. "No one wants to shoot someone, but faced with a deadly force situation, their options are limited. In a situation like that, you have three-fourths of a second to realize and act on the danger."
All law enforcement agencies train officers in the appropriate use of deadly force at least quarterly, said Raymond Foster, a retired Los Angeles police officer and former Petaluma resident. Officers are taught to fire in three-round bursts, he said.
Training involves simulations in which targets representing bad guys or innocent bystanders spin around and an officer has to decide whether to shoot, Foster said.
"The officer gets experience in making this quick decision in defending their life," he said.
Experts say that training has evolved in the past two decades as mass shootings involving increasingly younger gunmen have become more prevalent.
In the past, officers were trained to contain a gunman and wait until backup or a SWAT team arrived. Now, officers are taught to move toward the gunfire.
"Times have changed, and has forced police to employ more aggressive tactics," Foster said. "Twenty years ago, if you saw a 13-year-old with a gun, you'd think he's just out goofing off. But now we've had all these shootings done by very young children."
The day before the Lopez shooting, a Nevada 12-year-old shot and killed his teacher and wounded two classmates at school before killing himself.