Lachlan co-founded Zeira Corporation along with his wife. During his wife's pregnancy, he would commonly hold his hand on his wife's stomach, leading his daughter Savannah to believe her father was trying to hug her before she was born. He was described as being a funny man and a great man to work for by Matt Murch.
Lachlan Weaver was killed in a terminator attack on his helicopter. Official reports suggested that the crash that claimed Mister Weaver was based upon simple human error; however, Lachlan had been explained to have had over one thousand hours experience with the helicopter in question. The T-1001 disguised as Catherine Weaver detailed this story as well as the truth to James Ellison, in an effort to convince him to join Zeira Corp as a member of the Corporation's staff on a mission to find another terminator and capture it.
Employees of Zeira Corporation would voluntarily wear plaid on the anniversary date of his death in memory of their executive.