Authorities in Colorado and Texas are investigating two separate incidents that involved police officers shooting and killing teenagers.

In both cases, police said the teenagers threatened the officers. In both cases, families and friends of the teens have questioned the actions of police. And both shootings occurred amid an ongoing debate involving when and how police officers use force, a topic that has sparked protests across the country.

Last week, Kristiana Coignard was shot and killed by officers inside the police department building in Longview, Tex. Police said that Coignard, 17, walked into the lobby on Jan. 22 and “indicated” to officers that she had a gun.

One of the officers “determined she had a large butcher knife which she was attempting to pull out of her waistband,” and another officer also saw that she had a knife, police said in a statement.

When Coignard charged at one of the officers with the knife, another officer used his Taser “with no effect,” police said. Footage released by police on Wednesday showed Coignard charging toward one of the officers. Two officers fired their guns a combined four times, and Coignard was taken to a nearby hospital and pronounced dead.

Coignard’s aunt, Heather Robinson, told ThinkProgress that the teenager had been dealing with mental health issues. “I think it was a cry for help,” she said of Coignard’s death. “I think they could have done something. They are grown men. I think there is something they are not telling us.”

The Texas Rangers, a division of the state’s Department of Public Safety, are investigating the shooting, and the Longview officers involved have been placed on paid administrative leave. When the investigation is complete, the case will be given to the office of Carol Dorrough, the Gregg County district attorney.

This week, two officers in Denver were also placed on administrative leave after a shooting. On Monday, Denver police said that two officers had shot and killed Jessica Hernandez, 17, that morning.

According to police, the officers were walking up to an occupied, stolen car when the vehicle was driven into one of the officers. The officers shot Hernandez, who was taken to the hospital and pronounced dead.

“How can they shoot her when she doesn’t have a gun?” her father, Jose, said, according to the Denver Post.

The shooting is being investigated by the Denver Police Department, the office of Denver’s district attorney and the Office of the Independent Monitor, a civilian oversight agency. This agency has said it will look at the police department’s policies for shooting at moving vehicles.

Robert White, the Denver police chief, released a statement saying that the department welcomes “any input that can improve the way we serve our community.” His statement was accompanied by the department’s policy on shooting at moving vehicles, which states that officers shouldn’t fire at moving vehicles unless they believe it “poses an immediate threat of death or serious physical injury.”

“An officer threatened by an oncoming vehicle shall, if feasible, move out of the way rather than discharging a firearm,” the policy states.

The shooting has been followed by outrage in the community. A large crowd of demonstrators gathered outside a Denver police station on Wednesday to protest. The mother of another teenager in the car told the Associated Press this week that she saw officers pull Hernandez out of the car and place handcuffs on her. “She seemed like she was not responding, not moving,” Bobbie Diaz said.

These incidents have occurred as protests involving police tactics surged into the public consciousness following the deaths of Michael Brown in Ferguson, Mo., and Eric Garner in New York. During the protests that followed those episodes last summer, as well as others around the country, activists called for stronger oversight and investigations into cases where police use force.

The protests over police officers and how force is used have cropped up nationwide. In Albuquerque, the police department’s recent history of fatal shootings — officers shot and killed 27 people between 2010 and 2014 — has been the subject of heated protests. The Justice Department determined that officers there shot and killed people too often, saying in a report last year that Albuquerque police used deadly force at times when it was not needed.

In response to these protests, some officers and law enforcement groups have criticized the demonstrations and said they feel under attack; others, like the Nashville police chief, responded by saying the police must be “respectful of all people.”

Yet the larger debate has highlighted a related but separate issue: The uncertainty over just how often this sort of thing actually occurs.

There is no reliable, comprehensive data regarding how many times police officers shoot and kill someone each year. Attorney General Eric H. Holder Jr. earlier this month called for the federal government to pull together better information, saying that the current ambiguity is “unacceptable.”