This week, two black men were fatally shot by police officers — Alton Sterling in Baton Rouge, Louisiana, on Tuesday morning and Philando Castile Wednesday evening in Falcon Heights, Minnesota. Castile was shot inside his car after being stopped for a broken taillight.

Routine police stops like the one by the unnamed officer who pulled Castile over are not uncommon and, in fact, are often incentivized in police forces, as Jack Hitt of Mother Jones wrote in September 2015.

That’s a huge part of the problem.

In fact, NBC’s Tom Winter reports Castile was pulled over 31 times over his driving life, and received multiple tickets for a range of non-violent misdemeanors including "driving without a muffler" and speeding.

Hitt reported on the fact that many police departments assist city budgets in raising revenue — even funding police officers' salaries — through fines, tickets, and the added fees that accompany them. This cycle of perpetual fees, leading to mounting debt, disproportionately hurts black and brown communities, whose members are more likely to be stopped by police officers and more likely to be impoverished than white Americans. Hitt adds:

There is still no comprehensive study to determine just how many cities pay their bills by indenturing the poor, but it is probably no coincidence that when you examine the recent rash of police killings, you find that the offenses they were initially stopped for were preposterously minor.

When police depend on tickets to make money, it is reasonable to assume they will ticket more people. As Vox’s German Lopez pointed out, there is a racial disparity when it comes to the threat perceived by officers in these situations, which makes routine stops more dangerous for black Americans.

In police work, this bias can show itself when an officer stops a subject he views as a potential threat. Police officers are legally allowed to use force based on their perception of a threat, so long as their perception is defined as reasonable (usually as judged by a prosecutor, judge, jury, or grand jury). That doesn't, however, mean they always use force. "Police very often use a lesser level of force even when they’re justified at a higher level," [University of South Florida criminologist Lorie] Fridell said. But if some cops automatically consider black men more dangerous, they probably won't show nearly as much restraint against a black suspect as they would against, say, an elderly white woman. So police officers might be more likely to use deadly force against black people that's legally justified but perhaps not totally necessary.

When police specifically target black people and feel increasingly threatened as a result, we have instances of police brutality against black men and women.

Hitt writes that the first priority, then, should not be to eliminate the "bad cops" but to fight against the system that rewards them. "When the mission of the entire department shifts from 'protect and serve' to 'punish and profit,'" he writes, "then just what constitutes good police?"