One of the first officers to arrive on the scene of Wednesday's massacre at a San Bernadino, Calif. office building could only describe the scene that greeted him as “surreal” Thursday.

At a press conference, San Bernadino Police Lt. Mike Madden recalled entering the building with three other officers after hearing the dispatcher say, “we have an active shooter.” Almost a minute later, the officers discovered some of the 14 victims who died and the 21 others who were wounded.

“The situation was surreal,” Madden said. “It was unspeakable, the carnage that we were seeing, the number of people who were dead and unfortunately already died.”

Madden was on his way to lunch at around 11 a.m. when he heard the first calls about the incident, San Bernadino Police Chief Jarrod Burguan said. Madden’s words, coupled with police radio traffic, showed how quickly nearly 300 law enforcement officers arrived at the scene to get evacuated victims out of the Inland Regional Center and into triage tents, then into hospitals.

Burguan said at a late Wednesday press conference that he estimated it took about 15 minutes to get people evacuated from the scene once the first officers arrived.

“There was a very short response time, they did a follow-up very rapidly and got on top of the suspects,” Scott Reitz, a former Los Angeles Police Department SWAT officer instructor, told the Los Angeles Times. “I’m absolutely impressed. That sometimes takes hours or days.”

Madden said he and the other officers believed there were attackers still inside the building when they arrived. He described the scene as chaotic, with the air smelling of gun powder and alarms going off. The people inside had a look of “pure panic,” he added.

The two shooters were later identified as Sayed Farook, 28, and Tashfeen Malik, 27. Investigators believe the couple fled the scene before they could be apprehended. They would later be killed after a shootout on the streets of San Bernadino. Police said 23 officers from seven agencies were able to take them out.

The Associated Press contributed to this report.