Matt Kramer is Leah Keegan's secret lover outside her marriage to Jake Keegan. Kramer is also revealed to be the father of her son Tommy.
Despite starting the procedure for divorcing Leah, Jake was legally Tommy's father and had to pay child support and alimony. This enraged him enough to attack Matt and kill Leah. Jake attempted suicide but was restrained by state troopers and arrested, with Tommy being left in Matt's custody. (SVU: "Paternity")