New York (CNN) -- Four people were killed Sunday when a shooter opened fire inside a Long Island pharmacy, police said.
The shooting, which was reported to police shortly after 10 a.m. ET at Haven Drugs in Medford, was likely the result of a robbery, said Rob Busweiler, a spokesman with the Suffolk County Police Department.
Two customers and two employees are thought to be among the dead, he said.
CNN affiliate WPIX reported all the victims were shot "execution-style," in the head at close range.
Police believe one shooter was responsible for the violence. No arrests have been made, Busweiler said.
CNN's Max Markham contributed to this report.