He was killed by the same mob that shot and killed his partner Charles M McDaniel.

from FAG member Tenalquot:
-------------------------
"Shooting of McDonald and Gibson," Olympia Transcript, 29 January 1870.

The following telegram is from the Intelligencer and contains most of the
details we have learned concerning the shooting of McDonald and Gibson.

Steilacoom, January 23rd.

It appears in relation to the shooting yesterday that one B. Gibson, formerly of
Idaho, and who rumor said was an escaped murderer, some time since jumped the
land claim of Charles Wren of Victoria, and was made to vacate it by a Justice
court subsequently.

The same man rejumped the claim, was arrested and brought to trial on Friday
last before E. R. Rogers, Justice of the Peace, who granted Gibson a continuance
until Saturday, at l o'clock.

On Friday night it seems that Charles McDonald and said Gibson rode to several
farm houses in the county and threatened bodily injury to the owners among the
number McLain Chambers.

The impression now prevailed that said McDonald was an accomplice of Gibson's
and upon such impression the citizens of Muck Prairie formed themselves into a
vigilance committee, and started in pursuit of the jumpers.

Early on Saturday morning at a point about five miles from town, Gibson was
shot, supposed mortally, and was brought to the city. Meantime McDonald had
entered the city and made boisterous demonstration, and while doing so the
Vigilance committee came down with the body of Gibson and surrounded McDonald at
Westbrook's saloon.

McDonald disarmed himself of all weapons, excepting a large knife, and wanted to
make a statement but would not be listened to when one of the committee cried
"Shoot the son of a b------!"

McDonald then ran through the alleyway jumped over a railing and was making his
way out betweens Wood's law office (formerly) and Cates' building, when a ball
entered his left temple and he fell. After struggling about three hours, he
died.

Gibson in the meantime was taken up on to the hill beyond the jail, when lo and
behold he raised up and grabbed John Highstream's pistol and made fight, firing
two shots, the ball taking effect in the leg of John Legard and Highstream, but
wounding them very slightly. gibson was then shot through the head and died
instantly. The bodies were taken charge of by the Sisters of charity and will be
buried today.

The committee has abandoned their organization and returned home and thus has
ended a most deplorable trouble.

We learn further that sheriff Carson started from town for the place where the
first shooting occurred immediately upon hearing of it. At the garrison he, with
his deputies, were taken by the vigilantes and kept under guard during the day.

The funeral took place on Monday, the bodies being buried at the garrison
graveyard.