"Make sure you cover him from all sides," Ryu instructed on the phone.
After they sat down in their car and got their mobiles back he had been busy in calling his security teams and arranging all kinds of security in disguise and cover Shawn's car from all sides. He had been informed about the probability of Shawn's accident and to prevent it he had instructed to keep Shawn's car covered from all sides.
Shawn's car was in the middle of Ryu's and Dean's cars, Ryu kept his car behind to keep an eye on all sides of Shawn's car while Dean's car was in front. This way Shawn's car was safe from front as well as from the back side from any kind of accident.
Ryu wanted to make sure that Shawn will arrive to their house unscathed, and to achieve this, his security cars were maintaining their closeness to Shawn's car left and right. This was all the suggestion of Rita.