We all die, a lot us rapidly when the water keeps moving across the rock that just stopped and super tsunamis a good portion of the planet. The rest of us die slowly as the weather patterns are ruined for likely decades or centuries and we starve due to crop failures and the fact that the worldwide logistics we depend on is forever gone.
Edit: actually I thought some more, if it’s sudden then we’re all crushed by flying into the air into stuff at 1000 miles an hour when the rotation stops. If it’s gradual then we all starve since the weather is ruined