The activist group, known as Killed By Police, logged about 1,500 police-involved deaths between January 1, 2014, and April 30, 2015 in the US, according to a compilation made by the news website Vocativ.
The actual figure, however, could be much higher than 1,500, as it only includes confirmed police killings.
The activist group, which was founded on May 1, 2013, uses corporate news reports to log the number of people killed by nonmilitary law enforcement officers, whether in the line of duty or not, and regardless of reason or method.
Inadequate official data about police killings has prompted a number of activist groups to begin compiling their own statistics by using crime statistics and media reports.
The latest data comes as police departments across the United States are under increased scrutiny following a series of deaths of unarmed black men at the hands of white officers.
Large-scale protests have been held around the country against police brutality and racial injustice during the past year.
The recent unrest in Baltimore over the death of Freddie Gray, who suffered a fatal injury while in police custody, was the most violent in the country since the protests in Ferguson over the fatal police shooting of Michael Brown.
According to a recent analysis by The Washington Post and researchers at Bowling Green State University, just 54 officers were charged in the past decade for fatally shooting someone while on duty.
"These represent a small fraction of the thousands of fatal police shootings that have occurred across the country in that time," the Post said on April 11.