When they exited their vehicle after observing what was described as suspicious behavior, the officers were immediately fired upon by a male suspect, Harrison said.
One officer was struck and collapsed at the scene, while one or two officers returned fire, striking the suspect, according to Harrison.
McNeil, who had suffered multiple gunshot wounds, was rushed to an area hospital where he passed away, Harrison told reporters outside the hospital.
The suspect fled to a nearby building. New Orleans SWAT officers surrounded the building and were able to get the suspect to peacefully surrender, Harrison said.
The suspect, who is under arrest, was transferred to a nearby hospital and is receiving treatment for multiple gunshot wounds, according to police.
"We have lost one of our brothers. NOPD grieves this morning," read a tweet on the New Orleans Police Department's Twitter account early Friday.
"This hurts, I can't begin to tell you how much this hurts," Harrison said.
He and New Orleans Mayor Mitch Landrieu met with McNeil's family.
"These are the worst kind of days for the city," the mayor said. "It strikes at the heart of the city."
McNeil had been on NOPD's force for three years, a statement from the department said. He leaves behind a wife and two young children.
The New Orleans Force Investigation Team will investigate the officer-involved shooting, according to department protocol, Harrison said.