On 12th of February 1855, Constable Knibbs and mail carrier Septimus Toovey relieved Police Trooper McGuire who had escorted prisoner Obidiah Stevens from Albany to Beaufort Hills Police Station, enroute to the Perth Hospital.

Constable Knibbs was not advised that Stevens was suffering from an unsound mind. 

As they approached Williams, the party stopped to attend a watering hole, but Constable Knibbs had left is service pistols near the cart, and when they returned, he was immediately shot by Stevens through the heart at point-blank range, killing him instantly. 

Toovey ran for help and returned with Mr Granger who lived nearby, they both returned and overpowered Stevens. Toovey rode back to Beaufort Hills Police Station to request assistance from Police Trooper Maguire, who conveyed Stevens to Perth. 

Constable Knibbs was buried at the side of Albany Highway, Bannister on 13th of February 1855.

Constable Knibbs was survived by his wife who was pregnant at the time.