Update rows which match another table using Stored Procedure in SQL Server

ALTER PROCEDURE [dbo].[sp_shipment_assignment]

AS
BEGIN
SET NOCOUNT ON; 
DECLARE @id int
DECLARE @end_date_time datetime
DECLARE @vehicle_id int
DECLARE @begin_date_time datetime
UPDATE shipment_assignment SET end_date_time = @end_date_time 
(SELECT date_time from event_with_location where vehicle_id = @vehicle_id and date_time >= @begin_date_time)
WHILE EXIST (select @end_date_time from event_with_location)
BEGIN
Update shipment_assignment set end_date_time=@end_date_time , active = 0, 
END

here my sample .but its still getting wrong