The machine used in the incident was a
Komatsu D355A bulldozer
[9] fitted with makeshift armor plating covering the cabin,
engine and parts of the
tracks. In places this armor was over 1 foot (30 cm) thick, consisting of 5000-psi Quikrete
concrete mix sandwiched between sheets of
tool steel (acquired from an automotive dealer in Denver), to make ad-hoc
composite armor. This made the machine impervious to
small arms fire and resistant to
explosives: indeed three external explosions and more than 200 rounds of
ammunition fired at the bulldozer had no effect on it.
[1]
For visibility the bulldozer was fitted with several
video cameras linked to two
monitors mounted on the vehicle's dashboard; the cameras were protected on the outside by 3-inch (76 mm) shields of bullet-resistant plastic.
[1] Onboard fans and an air conditioner were used to keep Heemeyer cool while driving, and compressed-air nozzles were fitted to blow dust away from the video cameras. He had made three gun-ports, fitted for a .50 caliber sniper rifle, a .308 semi-automatic, and a .22 long rifle, all fitted with a half-inch-thick steel plate. Heemeyer apparently had no intention of leaving the cabin once he entered it.
[1]Authorities speculated he may have used a homemade crane – found in his garage – to lower the armor hull over the dozer and himself. "Once he tipped that lid shut, he knew he wasn't getting out", Daly said. Investigators searched the garage where they believe Heemeyer built the vehicle and found cement and armor steel.
[1]
