2008 gmc sierra alarm keeps going off

my friend just bought a 2008 gmc sierra and the alarm keeps going off and the truck is pretty much in shut down. cant start it cant do anything. we’re trying to figure out how to fix this problem. we arent sure if its because of the key fob? we tried putting a new battery in the key fob, still nothing. when you go to start the truck it wont even turn over and the alarm keeps going off. also the key fob only turns on but doesnt actually do anything.