The Sunday shooting in Baton Rouge, Louisiana, that left three officers dead began with a report of someone walking with a rifle. Within 10 minutes, there was a report of "officers down" and emergency responders were arriving at the scene.

The tragic shooting left three law enforcement officers dead and three other officers wounded. Police killed the suspect, a former U.S. Marine.

Images released by Louisiana State Police show suspected gunman Gavin Long in Baton Rouge, Louisiana, on July 17, 2016.(Louisiana State Police) Images released by Louisiana State Police show suspected gunman Gavin Long in Baton Rouge, Louisiana, on July 17, 2016.

As investigators search for a motive, here is a minute-by-minute break down of how the Sunday morning shooting unfolded, according to Louisiana State Police Superintendent Col. Mike Edmonson.

8:40 a.m Local Time

At about 8:40 a.m., Baton Rouge police officers at a convenience store in the Old Hammond area saw a man "wearing all black standing behind a beauty supply store holding a rifle," Edmonson said Sunday.

Images released by Louisiana State Police show suspected gunman Gavin Long in Baton Rouge, Louisiana, on July 17, 2016.(Louisiana State Police) Images released by Louisiana State Police show suspected gunman Gavin Long in Baton Rouge, Louisiana, on July 17, 2016.

8:42 a.m.

At about 8:42 a.m., there were reports of shots fired, Edmonson said.

In this aerial photo, investigators work the shooting scene in Baton Rouge, Louisiana, where several law enforcement officers were either shot or killed, July 17, 2016. (Gerald Herbert/AP Photo) In this aerial photo, investigators work the shooting scene in Baton Rouge, Louisiana, where several law enforcement officers were either shot or killed, July 17, 2016.

8:44 a.m.

At about 8:44 a.m., reports were received of officers down at the scene.

8:45 a.m.

At 8:45 a.m., there were reports of more shots fired, he said.

A chilling call into the East Baton Rouge Parish Sheriff scanner said, "Shots fired, shots fired, shots fired. I’ve got an officer down."

"I’m hit, I’m by the car wash," one officer said, according to police scanner audio.

"Two down back here, two down," another said.

8:46 a.m.

At 8:46 a.m., there were reports of the suspect wearing all black, standing near a car wash next to the convenience store, Edmonson said.

Images released by Louisiana State Police show suspected gunman Gavin Long in Baton Rouge, Louisiana, on July 17, 2016.(Louisiana State Police) Images released by Louisiana State Police show suspected gunman Gavin Long in Baton Rouge, Louisiana, on July 17, 2016.

8:48 a.m.

At 8:48 a.m., emergency responders began arriving at the scene to help the victims, he said.

The suspect, 29-year-old Gavin Long of Kansas City, Missouri, was shot and killed at the scene, Edmonson said.

The officers killed in the attack were Brad Garafola, 45, Montrell Jackson, 32, and Matthew Gerald, 41.

East Baton Rouge Sheriff Sid Gautreaux said the shooter was “definitely targeting police officers.”

"This is truly a sad day in Baton Rouge," Mayor Kip Holden said Sunday.

"We continue to ask the question and continue to make the statement, let peace prevail in Baton Rouge and this parish," he said. "We must look ahead."

Holden told ABC News this morning that police agencies across the country "should be on alert" and urged citizens to be vocal about their support for law enforcement.

"Make sure we embrace [police]," Holden said. "Let them know we love them. Let them know we appreciate what they are doing."

The Louisiana State Police Department is investigating.

Louisiana State Police released this image, July 18, 2016, of the weapons recovered from suspected gunman Gavin Long.(Louisiana State Police) Louisiana State Police released this image, July 18, 2016, of the weapons recovered from suspected gunman Gavin Long.