Should i notify the authorities?

i was riding the bus today and like every day i was sitting in the front, i heard a scream from the back of the bus while a older girl from the back of the bus was pointing outside the window, 2 men were standing over another bloody man, the one about to hit him again with his baseball bat. The other pulls out his gun and shoots him two times they hop in the car and drive off, i came home in deep shock, told my mom what happened and she replied "Your movin' with your auntie and uncle in Bel Air" , i whistled for a cab and when i came near......