Institutional Sneak Attack on XLI

I spotted some very high volumes coming in right at the end of market close and during after hours trading on XLI. Massive volumes = institutional traffic. However, price levels didn't actually move much until late into AH trading, when a tiny amount of volume (orders totaling 102 only) did a gap up in price to $63.88. This suggests a gap up breakout could occur, but this also feels heavily manipulated, so be careful here. I wanted to raise awareness of this movement and will be closely monitoring XLI on Monday.