Mehserle shot and killed 22-year-oldOscar Grant on New Year's Day 2009.
Grant was unarmed and lying face down at the time.
Friday, Mehserle released a letter to Grant's family apologizing for the shooting. It was written prior to his conviction.
"I know a daughter has lost a father and a mother has lost a son. It saddens me knowing that my actions cost mister grant his life...no words can express how truly sorry I am," Mehserle stated in the letter.
"This is a letter that was purposely designed to influence the judge as well as the jurors to bring about what he got. Sadly to say, we're not buying it as a letter of apology to us," said Grant's uncle Cephus Johnson.
Mehserle claimed that he mistakenly drew his gun instead of his Taser.
He is scheduled to be sentenced in August and faces anywhere from probation to 14 years.