Kayleigh then drove off with the trapped Carlton, only to eventually run out of gas. She called Dave, who made a pact with her to always help her without question when she needed it. So he came, filled the car and drove it away. The next day, Dave realizes that the car is reported missing, but instead of getting angry, he decides to dispose of it by pushing it into the river – unaware that Carlton is still in the trunk. Carlton died in the water, trapped in the car.
https://www.distractify.com/p/who-killed-carlton-stay-close Who Killed Carlton Flynn at the End of ‘Stay Near’? (SPOILERS)