Vankeuren, 37, of Emmaus was convicted of killing Audrey Giannotti in her basement apartment in the 2000 block of Earl Street on Jan. 13, 2007.
Berks County Judge Paul M. Yatron rendered the verdict following a two-day bench trial.
First degree-murder carries a mandatory sentence of life in prison.
Witnesses testified Vankeuren admitting killing Giannotti, who was sleeping in her apartment with her two young children, Jaliyah, then 3, Jamora Haynes, then 11 months.
Giannotti died of a gunshot wound to the head, medical officials said.
The murder remained unsolved until March 15, 2011, when Vankeuren was arrested in his residence.
Assistant District Attorney David Golberg called numerous witnesses who said Vankeuren admitted to the slaying.