Should I take this death threat seriously?

Im a freshman in high school. This kid that goes to my school and is in my pe cl said I was going to die. Hes a fat kid that nobody really likes. I try to be nice to him, and have been, except one time when we were in the locker room changing and a kid was taking a piss and looked over at the kid and said to his friend "I cant take a piss, this fat f!@#s watching me." and I couldnt help but laugh because he was staring at the guy taking a piss. Anyways, friday I was talking with a group of friends and one of them said something funny so I laughed, but I was looking at him when i laughed and he thought I was laughing at him. He came up to me and pushed me and I said "jeez, theyre getting pissy today." Later in the cl he came up to me and said "your going to die." and then walked away. I normally wouldnt take this seriously but with the school shootings and stuff I just dont know. Should I take it seriously or not?