Use the S.T.A.R.S Card in the computer in the main entrance of the Police
Station. When you get the S.T.A.R.S Emblem Key, go to the S.T.A.R.S Office.
When you are in the office, go to the big locker next to the
out-of-commission message receiver. Open the locker and you will get a
Grenade Launcher. Some people may find the Magnum in the big locker. In this
situation, the Grenade Launcher may be found in the Sub-Station.