Mary Branch is a senior resident in internal medicine at the University of North Carolina School of Medicine.

Knock knock.

Who could that be? I wondered. It was such an aggressive knock — definitely not friendly — that I froze. I finally stood up and walked to the door. I opened it with purpose, ready to confront the person on the other side.

He said: “Your neighbors called the police for a disturbance.

It was 3 p.m. on a Saturday last fall.

An hour before this unexpected visitor, I had been admiring a beautiful sunny day in Chapel Hill, N.C. — finally, a day off from my residency in internal medicine. I’d recently found out not only that I had been accepted to a cardiology fellowship but also that I was pregnant! My husband and I are newlyweds, and this was our dream.

I wanted to celebrate by putting some ’90s pop and hip-hop on the stereo. I started singing and dancing around the apartment. When a song had a lot of bass, I turned down the volume so as not to disturb anyone. I had not played this kind of music in a while. If I play it in the car, I often turn it down or off when driving near my neighbors or where I work. Although I hear other drivers blaring loud rock or country music all the time, I know an African American playing my type of music tends to draw negative attention. Nevertheless, this music was what I needed to embrace the joy I felt.

Hear the playlist the author was listening to here.

After about an hour, I had run through my playlist and started to wind down. I washed my hair and wrapped it. Dressed in comfortable clothes, I sat on the couch. I turned off the stereo and turned on CNN to catch up on the news.

Then came the knocks.

On my doorstep was a man with a gun; it was a police officer. He spoke abruptly and was frightening.

“Is someone else in here?” he said. His hand was near his hip, close to the gun in its holster.

“No, I’m alone,” I blurted, startled.

“I need to see your identification.”

“Why? I live here.” I felt bullied in my own apartment.

“I have to report this incident, and I need your identification.”

Feeling helpless, I reluctantly turned and walked to get the license out of my wallet. I handed it to him. “So what happens now?” I asked, deflated.

He explained that he would have to report the incident, but nothing really happens unless there is a repeated offense. I hardly felt listening to the Notorious B.I.G. at 3 p.m. on a Saturday was an “offense.” I’ve lived in many cities, and I could not imagine calling the police on a neighbor for anything like this. And I’m confident that my Caucasian neighbors would not have involved the police if some of the music they heard hadn’t been hip-hop.

I cannot prove that this was an act based on bias. But in studying and practicing medicine, I have developed skills in pattern recognition. They are well adapted to making a diagnosis of racism.

After that incident, I could not sleep for a few nights, because of how hurt I felt. Having a policeman approach and confront me left me feeling embarrassed, humiliated and powerless. I felt like an unwanted outsider in a community of which I thought I was a member.

Not long ago, two African American gentlemen were arrested in a Starbucks in Philadelphia while simply waiting for a colleague; I understand how fearful and helpless they must have felt. Then there was the woman wrestled to the floor by police at a Waffle House; I can relate to her likely feelings of anger mixed with submission. These scenarios aren’t new, nor are the emotions they stir up in us. As people of color, we’ve learned to present ourselves in an assimilated manner to shield ourselves from overpolicing. The poet Paul Laurence Dunbar described it best: “We wear the mask that grins and lies.”