The manslaughter trial of Peter Liang, the rookie cop who shot and killed 28-year-old Akai Gurley in a darkened housing project stairwell on Nov. 20, 2014, opened today.

In his opening statement, prosecutor Marc Fliedner told jurors a gripping narrative of that night — describing how Liang opened the stairwell door from the eighth-floor and fired into the dark at the exact moment Gurley and a friend entered from the seventh-floor after getting tired of waiting for the elevator.

Prosecutors tried to show Liang was reckless in the handling of his firearm in a stairwell that was routinely used by residents, including children.

But in her opening statement, defense attorney Rae Downes Koshetz called the Louis H. Pink Houses possibly the most dangerous project in the city. And she said there’s no rule against officers patrolling stairwells with their weapons drawn. Kosehtz described the shooting as a million-to-one mistake that left Liang distraught and in shock.

After opening statements, prosecutors played the 911 call from that night. It was the first time the chaotic call has been released publicly.

Testimony is expected to last through the end of next week. The jury could begin deliberations the week after.