Two men were shot and killed inside a Brooklyn apartment building, according to police, who are still looking for the gunman.

Officers were called to the building on Brooklyn Avenue in East Flatbush just before 11 p.m. Sunday, police said, following some type of argument. It was not clear what the argument was about, but it ultimately led to gunfire.

Detectives said the 47-year-old and 27-year-old victims were found in a fourth-floor hallway with gunshot wounds to the head and body. Investigators seen going in and out of the building were working to determine the connection between the pair.

According to the investigation, which was still in its early stages, it appeared the two victims were arguing with each other when a third person, the shooter, stepped into the feud and opened fire on both of them. The suspect then took off right after and was seen leaving the area, law enforcement told NBC New York.

The alleged shooter was described as a bald man wearing a blue jacket and jeans. The NYPD's K-9 unit had been called in to help with the search.

No arrests have yet been made.

What happened just before this tragedy, as police search for the person responsible. as we bring you back live… at this hour… it is still unclear what exactly was the argument that led to this episode of gun violence