On Tuesday, police in El Cajon, California, shot and killed 30-year-old Alfred Olango after his sister called 911 for medical assistance because her brother was suffering a seizure. Police say Alfred was acting erratically, but his sister says he was mentally disabled and had just had a seizure. Unarmed and in need of help, Alfred is not alone.

As of July, police had killed at least 800 Americans in 2016, many of whom were people of color, disabled, or had a mental health condition according to Thinkprogress.org. These shootings ignited Black Lives Matter protesters across the country and sparked a desperate plea to officers quick to draw a gun. Alfred is not the only disabled person to be killed by police. A report released by the Ruderman Family Foundation says people who are disabled or have mental health conditions make up nearly half of all people killed by police. With the African-American community more likely to experience severe mental illness because of lack of treatment and other barriers, these people are particularly vulnerable to police violence.

As we all try to make sense of such senseless violence, here’s what you need to know about Alfred Olango, and what his death says about mental health and law enforcement.

What does a seizure look like?

Alfred’s sister said her brother was having a seizure when she called police asking for help, but police say Alfred was walking erratically in traffic and took something out of his pants pocket. From everything we see about seizures on TV or in movies, it might seem like it’s not possible for Alfred to have been having a seizure while doing all those things, but that’s actually not true. There are a bunch of different forms seizures can take.

According to the Centers for Disease Control, seizures can include the typical things we hear about like falling down, shaking, and loss of consciousness, but they can also be less noticeable. Symptoms of a seizure can also include rapid blinking, staring into space, confusion, and the temporary inability to respond to questions or take direction.

Seizures are caused by much more than epilepsy. Certain medications, head injuries, internal bleeding, low blood sugar, stroke, and much more can all result in seizures. People with autism are also likely to have seizures, with around one-third of all people with autism experiencing seizures according to Autism Speaks.

What does disability have to do with it?

To be clear, having seizures is not a mental disability or illness, it’s a neurological condition. But, Alfred’s sister did say he had a mental disability. If that’s the case – the details are still emerging – Alfred is yet another disabled person killed by police. The Ruderman Family Foundation report found one-third to one-half of all people killed by police have some sort of disability and according to The New York Times, 25% or more of people in police shootings have a mental disorder. That, as NBC points out, has drawn increasing attention to how law enforcement handles mental health and wellness, a part of a police officer’s job that has been growing over the years. In San Diego, 911 calls involving mental health grew 84% over the six years from 2009 to 2015, according a San Diego Association of Governments study. In the Washington, D.C. area, officers underwent training in 2015 to deal with the increase in mental health calls.

Educator and activist Leroy Moore says the problem is even bigger than these numbers recognize, though.