Editor's Note: Police later said four people were arrested after a fight involving two off-duty police officers. A massive police response could be seen at 31st Street Beach in Chicago on Friday afternoon, video showed. Stream NBC 5 for free, 24/7, wherever you are. WATCH HERE WATCH HEREAround 4:20 p.m., aerial footage captured by NBC Chicago Sky 5 showed authorities swarming part of the parking lot for 31st Street Beach near the city's Prairie Shores and Lake Meadows neighborhoods. At least 15 marked Chicago police vehicles, an ambulance, fire truck and a large crowd of officers could be seen near the roundabout off East 31st Street near the Edwin C Berry Playground, video showed.