By Andrea Lucia

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DALLAS (CBSDFW.COM) – The second floor hall at El Centro College is still riddled with bullets from the July 7 ambush that left five police officers dead and 11 people wounded.

Its ceiling is still damaged from the explosion delivered by a bomb robot, which killed sniper Micah Johnson in the early hours of Friday, July 8.

“There was nowhere for him to go,” said Dallas County Community College District Police Chief Joseph Hannigan.

Hannigan Tuesday retraced gunman Johnson’s last steps during a walk-through of the downtown campus on Tuesday afternoon.

Hannigan said Johnson first approached two officers outside the college’s Lamar entrance. After a brief conversation, he pulled his gun and shot them both. Johnson then took cover behind the school’s pillars, shooting and killing DART officer Brent Thompson.

Johnson shot out the doors on Lamar Street, but was forced back by police gunfire. He then rounded the corner to Elm Street, shooting out doors there, making his way inside the college.

Two El Centro officers found a trail of his blood leading to a stairwell. When they opened the door, Johnson fired on them, pushing them back out.

Newly patched walls along those stairs show where Johnson’s bullets struck that violent night.

“He didn’t care who was in his way, but his focus was on police uniforms,” said Hannigan.

Johnson eventually retreated to the second floor library, according to Hannigan. He fired through the windows there, shooting out glass walls at the 7-11 convenience store across the street.

Dallas officers were pinned down, taking cover behind their cars.

“He was shooting for any officers that would move,” said Hannigan.

Police returned fire, forcing him to end of the hall. Unwilling to surrender, Johnson released a stream of bullets, preventing officers from making a safe approach.

Police Chief David Brown said the robot-delivered bomb was the only way to end the gunfight without risking more police officer’s lives.

(©2016 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)

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