ATMORE, Ala. — A lawyer for an Alabama inmate put to death by lethal injection said Friday she is concerned his trembling limbs and labored breathing were an indication something “was not right” with the procedure.

Robert Melson, 46, was pronounced dead at 10:27 p.m. CDT Thursday at a southwest Alabama prison, authorities said.

Melson’s attorneys had filed a flurry of last-minute appeals seeking to stay the execution, arguing that the state planned to use a sedative that would not reliably render Melson unconscious before other drugs stopped his longs and heart. In December, an Alabama man coughed and heaved for the first 13 minutes of an execution and appeared to move slightly after two consciousness tests.

“I don’t think there any questions that there was something that was not right,” said Christine Freeman, the executive director of the Federal Defenders Program in Montgomery, who witnessed the execution. “There is no question that midazolam is really problematic,” she said.

Melson’s hands and arms quivered and shook against the restraints at 9:59 p.m. His breathing appeared to become labored, with his chest moving up and down, before slowing until it was no longer perceptible by 10:09 p.m.

The execution took 32 minutes from the time the death warrant was read until Melson was pronounced dead at 10:27 p.m. CDT.

The Alabama attorney general’s office argued midazolam’s use has been upheld by the U.S. Supreme Court and it has allowed multiple executions to proceed using the drug, including the execution of an Alabama inmate last month.

The execution was the state’s second of the year.

Corrections Commissioner Jeff Dunn said Thursday that Melson’s execution went according to protocol.

State prosecutors said Melson and another man who used to work at the restaurant, robbed a Popeye’s in Gadsden, 60 miles (96 kilometers) northeast of Birmingham, and Melson opened fire on four employees in the restaurant’s freezer. Nathaniel Baker, Tamika Collins and Darrell Collier were killed. The surviving employee, Bryant Archer, crawled for help and was able to identify one of the robbers as the former worker which led police to Melson.

Collins’ family members wore a badge with her photograph and the phrase “In Our Hearts Forever.” Her family issued a statement saying that three young people lost their lives for “a few hundred dollars” and criticized claims that the state’s execution procedure as inhumane. Collins’ mother and two sisters witnessed the execution.

“He has been on death row for over 21 years being supported by the state of Alabama and feels he should not suffer a little pain during the execution. What does he think those three people suffered after he shot them, leaving them in a freezer?” the statement said.

Melson rocked his head no when the prison warden asked if he had a final statement at around 9:55 p.m. and a prison chaplain knelt beside him as the lethal injection began.

“Robert Melson’s decades-long avoidance of justice is over. For twenty-three years, the families of the three young people whose lives he took, as well as a survivor, have waited for closure and healing. That process can finally begin tonight,” Attorney General Steve Marshall said in a statement after the execution.