LENEXA, Kan. (AP) — Investigators found pipe bombs and a GPS tracking device in a car outside a Lenexa home where police say a gunman killed his ex-girlfriend and a man she was dating before then killing himself.

Investigators also found a so-called ghost gun and other weapons inside the home where Sara Beck, 22, of Belton, Missouri, and John Williamson, 20, of Lenexa, were killed early Sunday morning, television station WDAF reported.

Police have said the gunman was Dustin Johnson, 37, of Belton, who also killed himself. Police say Johnson had previously dated Beck.

According to court documents, Johnson was wearing a tactical vest when his body was found. Police also found an assault rifle near Johnson's body that had been constructed from various parts and had no serial number.

Police said they believe Johnson was using the tracking device to keep tabs on his ex-girlfriend.

Court records show police later found black powder, ammunition, books on bomb building and other items to make bombs in Johnson’s duplex in Belton. Johnson's neighbors told television station KCTV that police evacuated them Tuesday before searching Johnson’s duplex.