Parkland Mass Shooting Police Audio: 'I Think We Have Shots Fired'

(CBS) -- Police dispatch exchanges in the moments after the mass shooting at Marjorie Stoneman Douglas High School were released on Thursday, revealing the chaotic minutes during the attack.

Based on a timeline released with the recordings, Nikolas Cruz allegedly began shooting about a minute after entering the building at 2:21 p.m. He was inside the school for about six minutes.

Within two minutes after Cruz was seen entering the school on Feb. 14, the sheriff deputy on duty at the high school, Scot Peterson, reported: "I think we have shots fired, possible shots fired."

At the same time, the Fire Department has been sent to the scene.

Peterson is seen on video surveillance at 2:23 p.m. on the outside of the building.

At that point, he tells dispatch: "Make sure we get some units over here!" He appears to remain at this location during the entire event.

Peterson later resigned after it was learned he never entered the school to try to stop the shooter.

At 2:25 p.m. other officers who have arrived at the scene confirm more shots being fired: "I hear shots by the football field!" Shots fired by the football field!"

Police discover the first shooting victim at 2:28 p.m.: "I have the gunshot victim, I have the gunshot victim, he's by the entrance," an officer tells the dispatcher.

At the same time, another officer reports: "I had a parent tell me there is a child down ... a parent told me there is a child down, have rescue stage."

By this time, Cruz has already discarded the weapon, an AR-15, in a stairwell and is captured on video exiting from the west side of the building at 2:27 p.m.

At 2:30 p.m. he was seen on video on the southwest part of campus as authorities scramble to secure the school. Cruz was able to blend in with the crowds of students and eventually left, according to published reports in the days after the attack

The dispatch recordings released Thursday end at 2:33 p.m. as police began to evacuate the building where the shooting occurred.

Cruz was later seen entering a Wal-Mart at 2:50 p.m., where he spent about three minutes. He then went to a McDonald's at 3:01 p.m., for about one minute.

He was arrested by Coconut Grove Officer Michael Leonard at 3:40 p.m.

Cruz has been charged 17 counts of first-degree murder, which could mean a death sentence if he is convicted. The indictment returned by a grand jury in Fort Lauderdale also charged the 19-year-old with 17 counts of attempted murder for the Valentine's Day massacre.

Cruz's public defender has said he will plead guilty if prosecutors take the death penalty off the table, which would mean a life prison sentence, CBS News has reported. The Broward County state attorney has not announced a decision on the death penalty.

Here is the published timeline of events. (The pink colored entries represent moments captured on security video. Click on the images to enlarge.)