Singer Drake says he has been left "truly scared" about the "strained" relationship between police and black people after the shooting of a man in Louisiana.
Alton Sterling had been selling CDs outside a Baton Rouge convenience store when two white officers tried to arrest him.
His death was filmed on the mobile phone of an onlooker who said the shooting was another example of deadly force being used by police officers.
Reports said Mr Sterling, 37, had been brandishing a gun when he was shot in the chest and back but this was disputed by witnesses.
In an open letter posted on Instagram, Drake, who is Canadian but calls America his "second home", said the death had left him "disheartened, emotional and truly scared".
"It is impossible to ignore that the relationship between black and brown communities and law enforcement remains as strained as it was decades ago.
"No one begins their life as a hashtag. Yet the trend of being reduced to one continues."
#AltonSterling began trending on social media soon after the shooting on Tuesday morning.
Drake said he remained hopeful that "things can change for the better" and offered his condolences to Mr Sterling's family.
At a news conference on Wednesday, the head of the National Association for the Advancement of Colored People (NAACP) in Baton Rouge called for the police chief to be fired.
"What I'm calling for today is that the chief law enforcement officer to fire the police chief," Michael McClanahan said. "He must step down. We cannot have anybody who allows this type of action to take place."
Bruno Mars, Katy Perry, Susan Sarandon and Justin Timberlake are just some of the other celebrities to have commented on the shooting.