To my knowledge he either died of old age, or alcohol poisoning. To your second question, He died at the age of 81, on October 2, 1803. This is the reason why there's Samuel Adam's Beer! Hope this helps!
He didn't.
John Clayton Adams died in 1906.
John Adams Webster died in 1877.
John Adams Whipple died in 1891.
John Adams Harper died in 1816.
John J. Adams died in 1919.
John Jay Adams died in 1926.
John Adams Gilmer died in 1868.
John T. Adams died in 1939.
John Adams - cartographer - died in 1738.
John G. Adams died in 2003.
John Adams - educator - died in 1863.