While the murder of two New York Police Department officers in Brooklyn on Dec. 20 is still under investigation, some details have come to light in how officers were able to track down the man behind the shootings.

The murder was witnessed by two Con Edison workers, who were actually sitting at a red light when they saw 28-year-old Ismaaiyl Brinsley shoot the two officers, according to the NY Post. One called 911 while the other flagged down another patrol car.

Going above and beyond the typical duties of a fleet driver, the Con Edison workers then followed Brinsley in their truck to a subway station Brinsley entered, making sure to tell police where they saw him go, according to several news sources.

In reaching out to Con Edison for comment, because the investigation is still underway, the company couldn’t comment further about the drivers. “Right now, this is a time for grieving and it’s a time for the police department,” said Sydney Alvarez, a Con Edison spokesperson.

A detailed article on the incident can be found at New York Times.