-- First you can try the sysprocesses to get SPID and Kill Them
DECLARE @DB SYSNAME -- Put the name of database here
DECLARE @SPID VARCHAR(4), @cmdSQL VARCHAR(10)
SET @DB = 'Northwind'
-- Looks for all spids that are connected in the databases
DECLARE cCursor CURSOR
FOR SELECT CAST(SPID AS VARCHAR(4)) FROM master.dbo.sysprocesses
WHERE SPID > 50 -- To not try to Kill SQL Server Process
AND SPID != @@SPID -- To not kill yourself
AND DBID = DB_ID(@DB) -- To filter only the users connected in specific database
OPEN cCursor
FETCH NEXT FROM cCursor INTO @SPID
-- For each user connected in the database
WHILE @@FETCH_STATUS = 0
BEGIN
SET @cmdSQL = 'KILL ' + @SPID
-- Kill the user
EXEC (@cmdSQL)
FETCH NEXT FROM cCursor INTO @SPID
END
CLOSE cCURSOR
DEALLOCATE cCURSOR