Tuesday night in Oklahoma two men were scheduled to be executed.
Clayton Lockett, 38, was the first to be given the lethal injection.
Ten minutes after doctors administered the first drug, containing the sedative, he began to twitch and mumble.
He was pronounced unconscious at the time and the last two injections were given.
The second of the three step antidote contains a paralytic.
The third is what stops the heart from beating.
Witnesses said doctors closed the curtains to the public and Lockett was pronounced dead about an hour later.
Doctors said if the person is not sedated before the last two drugs are administered it causes agonizing pain and suffocation.
Missouri lawmakers said this incident in Oklahoma raises questions, but Governor Nixon points out the courts have upheld Missouri's current execution method.
This was the first time the state of Oklahoma has used the sedative Midazolam in a 3-drug combination.
32 states currently use the death penalty, and some are considering a review of their lethal injection cocktail.
Missouri Representative Linda Black said the state will need to take a step back and take a second look.
"Of course we want to revisit it. Make sure that Missouri is doing all we can to make sure we don't have any incident with executions and lethal injections that we have," said Black.
Black said there will be a lot of public attention when someone who is declared unfit to live in society is executed.
She said this is an issue Missouri needs to stay ahead of.
"I know that there's been some controversy surrounding what the state of Missouri uses for lethal injections. So yes, we do have a situation in the state where we have to look at where our pharmaceuticals are coming from."
Executions in Oklahoma have been put to a halt.
A second man was supposed to be executed Tuesday night, and that has been put on hold for 14 days until a full review of the injections used has happened.
ABC 17 News has not heard back from the Department of Corrections after multiple calls.