UPDATE: A source from within the Kettler Iceplex organization tells us that the deceased man is Brian St. Louis, a youth hockey coach. ARLnow gets the scoop that police are investigating a death at Kettler Capitals Iceplex in Ballston. Reportedly, a man in his 20s or 30s suffered some kind of medical emergency late this morning; after he was transported to the hospital, the man died. The Capitals, who use the facility for practices, were…