LA County Sheriff uses exclusively Tac-Ops. LAPD does not. FBI uses their home brews right now (made by USMC armorers at Quantico if memory serves me correctly).
Did the hostage survive? If so, then the sharpshooter did his job. He may not have instantly killed the subject, but apparently he instantly incapacitated him. Remember, that brain stem is about a 1" x 1" target. Now, throw in the fact that that 1" target is bouncing around, moving, is holding a hostage, etc. It is not a trivial shot. Subject could have turned his head the exact instance the trigger was pulled, etc. LA SWAT and LA Sheriff SEB are two of the most active and best units in the country... those guys are pros.
For good practice, fill up a helium ballon, put a 1" sticker circle on the ballon, tie it on your target with about 3-4 feet of ribbon at 100 yards on a breezy day (so its constantly moving around), and try and hit the circle sticker.
MEL