Sammy killed many of his friends including ones he had known since childhood, he had no moral compass. There were numerous witnesses to what Sammy did and it was why he was late to get away before the police arrived even though he had a getaway car waiting for him. As a result, he was detained and questioned for hours, in the podcast he's a little vague as to why he was late to escape questioning.
https://www.wikiwand.com/en/Sammy_Gravano