The Pima County Sheriff's Department amended its timeline of events surrounding the Jan. 8 shooting spree that killed six people and wounded U.S. Rep. Gabrielle Giffords and 12 others.

The first ambulance arrived at the scene at 10:20 a.m., nine minutes after the first 911 call reporting the shootings, the department said Wednesday. Previously, the Sheriff's Department had said the first ambulance arrived 11 minutes later at 10:31 a.m.

In an e-mail from the department's spokesman, Deputy Jason Ogan, the department also gave its first estimated time for when the scene was considered secure for medical personnel.

That was about 10:23 a.m., Ogan said.

Before that, medical responders were kept out of the scene while officers made sure it was safe.

The fire and medical groups that responded to the scene are planning to meet today to discuss their response and clarify the timeline, said Adam Goldberg, spokesman for Northwest Fire/Rescue.

The Sheriff's Department's new information is consistent with a timeline put together by the Rural/Metro Fire Department, which also sent equipment and personnel to the scene.

That department said the first medical personnel, from Northwest, arrived at 10:19 and the first ambulance, from Southwest Ambulance, arrived at 10:20.

By the time officers gave the "all clear" to enter, three ambulances were at the scene, says the Rural/Metro timeline: Two from Southwest and one from Rural/ Metro. In its entry for 10:31 a.m. the timeline also seeks to clarify the PCSO's original timeline, released Friday:

"The Sheriff's Department reports that Southwest Ambulance Paramedic 831 is the first ambulance on scene, but this turns out not to be correct. It's the fourth ambulance on scene. This ambulance had not been dispatched until 10:27.

"The sheriff's timeline may focus on this ambulance because it's the one that will carry Rep. Giffords."

That ambulance left the scene, carrying Giffords, at 10:41 a.m., 10 minutes after it arrived and 31 minutes after the congresswoman was shot. It arrived at University Medical Center at 10:54 a.m.

Contact reporter Tim Steller at 520-807-8427 or at