His time of death was 10:14 a.m.
“To know that he will never walk this earth again does give me a little more peace than yesterday,” said Shelli Milner.
Postelle was convicted of murdering Milner’s only brother, Donnie Swindle, as well as Amy Wright, Terry Smith and James Alderson on Memorial Day in 2005.
He believed Swindle was responsible for causing a motorcycle crash that injured his father. The other victims were at the Swindle mobile park home at the time.
“I will never have peace knowing what he did to my brother Donnie, to Amy, to James and to Terry,” said Milner.
During Thursday’s execution, when asked if he had any last words, Gilbert Postelle shook his head no.
Media witnesses described Postelle’s execution process as smooth.
“I would just say that the execution appeared to go off without any complications or problems,” said AP Sean Murphy.
She wishes Paul Howell’s family had the same feeling.
Julius Jones, who was convicted of killing Howell, was granted clemency last year.
“To the Howell family, you should have had the opportunity a few months ago and my heart goes to you,” said Milner.
Media witnesses stated Postelle’s body reacted quickly to the first drug, midazolam.
Department of Corrections Director Scott Crow later said the execution took place without complication.
Gilbert Postelle’s brother, David Postelle, was sentenced to life without parole for his part in the quadruple Memorial Day murder.
Their father, Earl Postelle, was declared incompetent to stand trial due to the injuries he had suffered in the motorcycle accident.
Gilbert Postelle was sentenced to death after evidence showed he followed Wright and Alderson and shot them from behind as they tried to run away.
Postelle’s execution is the last before the start of a federal trial later this month over Oklahoma’s lethal injection protocol. He was one of several death row inmates suing the state over the controversial protocol.