I thought I might flinch but I didn't. It was so quick that for a split second I think I wondered if it had actually happened.

There was no blood splattered across the white cinderblock wall at the Utah state prison. No audible sounds from the condemned. I couldn't see his eyes. I never saw the guns and I didn't hear the countdown to the trigger-pull.

A twice-convicted killer who had a troubled upbringing, 49-year-old Ronnie Lee Gardner was executed by firing squad shortly after midnight on Friday. I was one of nine journalists selected to observe his death, which the state classifies as a homicide.

But it wasn't like other homicides I had covered. In those instances the media showed up after the death, not before.

This, however, was a meticulously orchestrated event with a sober, prepackaged ending.

Inside the prison we walked in single file and were asked not to talk. We were restricted from bringing our notebooks and pens and from asking questions at certain times.

When the prison warden pulled back the beige curtain Gardner was already strapped into a black, straight-backed metal chair. His head was secured by a strap across his forehead. Harness-like straps constrained his chest. His handcuffed arms hung at his sides. A white cloth square – maybe 3 inches (8cm) across – affixed to his chest over his heart bore a black target.

Seconds before the impact of the bullets Gardner's left thumb twitched against his forefinger. When his chest was pierced he clenched his fist. His arm pulled up slowly as if he were lifting something and then dropped. The motion repeated.

Although the dark blue prison jumpsuit made it difficult to see, blood seemed to be pooling around his waist. The silence was deafening.

A medical examiner checked Gardner's pulse on both sides of his neck, then lifted the black hood to check his pupils with a flashlight, offering a brief glimpse of the dead man's now ashen face.

It was 12.17am. Only two minutes had passed since the shots were fired but it felt like things had moved in slow motion.

About an hour later prison officials let the media inspect the chamber. There was a strong smell of bleach but no sign of blood.

The only evidence that a man had been shot and killed were four bullet holes in the black wood panels behind the chair. The distance between them was a few inches.

Prison officials say Gardner willingly made the 90ft walk to the execution chamber on Friday morning. That's hard to imagine, particularly of Gardner who, by his own accounts, had spent much of the 30 years he was incarcerated "obsessed" with escape.

Despite being surrounded by dozens of prison officials and witnesses he essentially died alone.

No one from his family watched him go. His attorneys were not present. He chose not to utter any final thoughts or feelings. Maybe it was his way of holding on to a small slice of privacy amid his very public death.

Jennifer Dobner witnessed Ronnie Lee Gardner's firing squad execution for the Associated Press.

• This article was amended on 21 June 2010. In the original we mis-spelt the word bullet. This has now been corrected.