Cell phone video shot inside El Centro College in Dallas the night of the attack shows police searching for gunman Micah Xavier Johnson who had already wounded officers outside before shooting his way into the building, according to NBC 5 Investigates.
"The doors exploded from gunfire. Two of my officers sustained injuries. One of them had glass fragments that entered his legs," said El Centro Police Chief Joseph Hannigan.
He said his officers continued to fight, helping Dallas SWAT officers who pursued Johnson to the second floor of the building during the gun battle, despite their injuries.
With the suspect cornered in an alcove on the second floor, SWAT negotiators took over ultimately using a bomb delivered by a robot to end the standoff.
Fifty-eight students trapped inside the building all survived the attack.