Stanley Cup Game 1 and NBA Eastern Finals game 3 running against each other, both in Detroit.Were the arenas filled to capacity?
Celtics v Pistons: Attendance: 22,076 (100% full, according to Wikipedia)
Pens v Wings: Attendance: 20,066 (100.0% full)
So, yeah, they supported them both. 
Tigers were sold out too.
was that the 19-3 game?
Yep.