ATLANTA -- Convicted cop killer Gregory Lawler, 63, was executed Wednesday just before midnight, less than an hour after the Supreme Court of the United States denied his last-minute appeal for a stay.

Lawler ambushed two Atlanta police officers on October 12, 1997 -- Officer John Richard Sowa, and Officer Patricia Cocciolone. He shot them both multiple times. He killed Sowa, and nearly killed Cocciolone, leaving her with permanent brain injury.

Reporters who witnessed the execution said it took 15 minutes from the time of the lethal injection to the time of death, which was 11:49 p.m. ET.

They said the witnesses included Officer Cocciolone, now retired; Officer Sowa's widow and sister; and Fulton County D.A. Paul Howard, whose office prosecuted Lawler, and sought the death penalty.

Lawler was convicted and sentenced to death in 2000.

The reporters were Greg Land of the Daily Report; Kate Brumback of the Associated Press; Jon Lewis of WSB Radio; and Rhonda Cook of the Atlanta Journal Constitution.

Brumback said Lawler did not make a statement and declined an offer of prayer.

Cook said Officer Sowa's widow and sister embraced, and rested their heads together, silently.

Lewis said Officer Cocciolone sat motionless, looking straight ahead at Lawler on the gurney.

Lewis said what struck him was how peaceful the process was compared to Lawler's horrific and murderous blast of gunfire at the officers 19 years and one week ago.

"I can still remember, people felt horrible" because of the shootings, as the impact began to sink in, Fulton County District Attorney Paul Howard said Tuesday. "There was a feeling of disbelief, and a feeling of utter pain."

Howard was on his first year as D.A. when this case came to his desk.

Lawler's court-appointed attorneys asked both the Supreme Court of Georgia and the Supreme Court of the United States to issue a stay because, the attorneys said, Lawler is on the autism spectrum, which was diagnosed only last month. They said that executing a man with lifelong autism would violate the 8th Amendment to the Constitution, which prohibits cruel and unusual punishment.

The Georgia Supreme Court rejected the appeal just before 7:00 p.m. Lawler's attorneys then took it to the U.S. Supreme Court, which denied the appeal just after 11:00 p.m.

According to the Georgia Department of Corrections, Lawler is the 67th Georgia death row inmate (66 men and one woman) executed since 1976 when the death penalty was reinstated. He is the 44th Georgia death row inmate executed by lethal injection. The previous 23 inmates were executed in the electric chair. Lawler is the seventh inmate executed in Georgia, so far, in 2016, the most ever executed in Georgia in one year, since 1976. There are now 60 inmates on Georgia's death row.