What happened

An oil-and-gas flowline severed during nearby home construction in 2015, but incorrectly recorded as abandoned, had been leaking natural gas into the soil for months; the gas migrated into a home's basement and ignited while two men replaced a water heater, killing both instantly. The NTSB found the well operator's abandonment records were wrong and faulted the town of Firestone for approving the housing development near the well without adequate pipeline mapping. This was an accidental infrastructure failure, not an attack.

When cited sources give different casualty, damage or spill figures for this event, they’re reported side by side above rather than merged into one number. See how confidence levels work.