Core Points - A mass shooting occurred in Fairmount Park, Philadelphia, resulting in 2 fatalities and 9 injuries, including 3 teenagers aged 15 to 17 [1] - The incident took place after a car meet, with the park being crowded due to Memorial Day celebrations [1] - The police are investigating the shooting, focusing on social media and shell casings to determine the number of shooters and the type of weapons used [2] Group 1 - The shooting involved rapid-fire or fully automatic weapons, potentially modified from standard semi-automatic handguns, capable of firing 17 rounds in 2 seconds [2] - Fully automatic handguns are increasingly common in gun violence investigations in Philadelphia, with parts being easy to assemble and difficult to detect, even potentially 3D printed [3] Group 2 - Glock handguns, produced by Glock GmbH, are prevalent in law enforcement, making up 40% of police firearms in the U.S., due to their affordability and ease of modification for criminal use [5] - A previous incident in Harlem, New York, involved a shooter using a Glock handgun, highlighting its association with gun violence [5]