Trump’s comments came after the Virginia measure passed by a slim margy of 51.4 in favour and 48.5 against.
This vote is part of a wider national fight between Democrats and Republicans over gerrymandering.
The new maps in Virginia could make it easier for Democrats to take control of the US House of Representatives in November.
The race is tight, and a win could result in more seats in Congress for the Democrats.
US officials believe the shooting related to the Democratic politician's ongoing divorce with Cerina Fairfax, a dentist.
Investigators say Justin Fairfax shot his wife, Cerina, multiple times before turning the gun on himself.