[UPDATE: The successful T-38 kill occurred within the last three months at Holloman AFB, NM, says Lt Col Lloyd Addison, chief of the USAF's T-38 sustainment office.
That means the aircraft is from the same black-painted T-38 unit that escorted F-117s before they were retired. Now, the Holloman T-38's provide proficiency training for F-22 pilots, among other tasks. It seems likely that an experienced F-22 pilot was in the cockpit of the T-38.]
The facts are a bit sketchy here. This clip was posted to YouTube on 18 April by an anonymous user named "d43e49". The video identifies the attacking aircraft as a T-38, but it's not confirmed by anything shown within the clip. At the 35-sec mark, the F-22's shape is clearly visible as it emerges above the target sight after the kill.
As far as I know, this is the first video clip of a simulated F-22 shootdown to reach the public domain. That is newsworthy by itself. Let's also be very clear: a single simulated kill without context says nothing meaningful about the F-22's dogfighting or aerial prowess. Even an EA-18G can apparently get lucky once.
If a T-38 was really involved, then congratulations to the pilot. Your are either absurdly lucky or insanely skilled.