PHILADELPHIA (CBS)  - Teen brothers, 13 and 17, were shot and killed in the city’s Overbrook Park neighborhood Tuesday night, according to authorities.

The shooting happened inside their home in the 1300 block of Westbury Drive at about 7:30 p.m. Authorities say the shooter entered the home and fired multiple times with what may have been a .45 caliber handgun.

Investigators say the 13-year-old boy was shot in the head and pronounced dead at the scene. The second victim died at the Hospital of the University of Pennsylvania a short time later after being shot in the head and torso, according to police.

As of late Tuesday evening, police are not sure the teens were targeted. Their names have not yet been released.

Chief Inspector Scott Small believes the shooting may be drug-related because narcotics were found at the scene. Homicide investigators are interviewing several adult males who were also in the home at the time of the shooting.

A search for the suspect is underway. He is described as a white male, approximately 5’8″ tall. Authorities say he fled northbound on Westbury Drive.

The investigation is ongoing.