KING OF PRUSSIA, Pa. (CBS) – A 23-year-old Upper Merion man has been ordered to stand trial on charges that he stabbed his mother, his father, and his twin brother to death in their King of Prussia home last March.

A Montgomery County detective testified today that when he questioned Joseph McAndrew Jr. about what happened the night his parents and brother were found dead in their home, he replied “extermination.”

When asked who, the detective recounted, McAndrew had replied eerily, “Person named father, person named mother, person named brother.”

McAndrew will stand trial on first-degree murder charges.  Prosecutor Kate McGill says there’s compelling evidence.

“The defendant was covered — I believe the word that they used was saturated — with blood from his knees down, and his shoes were covered with blood,” she told KYW Newsradio today.

Police say a sword, believed to be the murder weapon, was found in the Holstein Road home.

McAndrew was recently ruled competent to stand trial but is still being treated at Norristown State Hospital for mental illness.

Defense attorney Denise Marone says they haven’t decided how they will proceed with their case.

Reported by Brad Segall, KYW Newsradio 1060

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