Austin police Lt. James Nisula tells Associated Press Radio the man boarded the bus Saturday and ordered the bus driver to get off.
The Austin American-Statesman reports he also forced two passengers to leave the vehicle before getting behind the steering wheel and driving away.
Police spotted the bus and pursued it. They tried several times to get the driver to pull over, but he refused.
Nisula says officers put down road spikes and deflated the bus tires. He says the man eventually pulled into an auto parts store parking lot, where he fatally shot himself.
Police didn't immediately release the man's name.
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