U.S. Park Police Officer Carl Hiott is one of two officers who shot and killed Aaron Alexis at the Navy Yard on Sept. 16, 2013. (Sarah L. Voisin/The Washington Post)

At 9:15 a.m., the near-hour-long search through 600,000 square feet of office space narrowed to a single corridor, six rows of cubicles and a smattering of offices of Building 197. Aaron Alexis was hiding amid the cluttered desks and six-foot partitions.

The mass killer at the Washington Navy Yard had just shot a police officer in both legs, and Dorian DeSantis and Carl Hiott saw their wounded counterpart being dragged out. The officers were heading toward the same spot, a confrontation imminent.

“We finally knew where he was,” Hiott said.

The two were from different agencies and different generations. They had never met before this moment, at the entrance to the amphibious warfare division.

The 50-year-old DeSantis, a veteran with two dozen years behind him, turned to Hiott, 29, and quietly asked whether he had active-shooter training. Hiott, just three years from the academy, nodded yes.

Remembering the Navy Yard victims

“Let’s go,” DeSantis said.

DeSantis, assigned to the D.C. police tactical team, was dressed in paramilitary gear and helmet and carried an AR-15 assault rifle. Hiott, a U.S. Park Police officer, assigned to protect monuments and parks, had come from investigating a parking complaint and was in a light blue, short-sleeve patrol shirt pulled tight over a bullet-resistant vest. He clutched an M4 rifle.

The two were among 117 officers from eight agencies who quickly formed into teams on Sept. 16, 2013, and went to find Alexis, and arrest or kill him. They were thrown together again by fate, strangers made partners amid the chaos of a colleague falling to gunfire. Their training had taught them this might happen, and neither hesitated to entrust his life to the other.

DeSantis and Hiott moved slowly down the corridor, third floor, west side, taking turns leaning around partitions and peering under desks. A fire alarm, pulled earlier by a worker trying to alert others to the danger, blared.

Alexis was beneath the last desk in the last row, under a banner that read, “Don’t give up the ship.” He had killed 12 people, primarily with a pump-action Remington shotgun in the first six minutes of his rampage, and all of them within the first 22 minutes.

“He came up and started firing,” Hiott said.

One bullet struck DeSantis in the center of his chest, lodging in his protective vest, though he didn’t know it at the time. Both officers returned fire. Together, they fired 51 rounds, according to an official reading from an internal report that has not been made public. Alexis was struck 17 times.

“One shooter down!” Hiott said over his radio.

Beyond the obstacles

Hiott agreed to share his story a year after the shootings, a rarity for officers who discharge their weapons, even more unusual when the result is fatal. D.C. police would not allow DeSantis to be interviewed.

The experience of officers and commanders that day has led D.C. police to institute some changes to better prepare for mass shootings. A District police critique of the response, completed months after the massacre, recommends giving D.C. officers shorter rifles, finding the AR-15s unwieldy in tight office space. Police are also getting earpieces, convinced that Alexis could hear the radio transmissions and used the sounds to elude capture or set up ambushes, and that such chatter betrayed D.C. Officer Scott Williams, who was shot in the legs.

Despite those obstacles, though, the interview with Hiott and the report show how officers came together amid a chaotic scene to navigate the massive building in their hunt for Alexis.

At five stories, Building 197 is the largest on the Southeast Washington installation. It houses the Naval Sea Systems Command — naval engineers who buy, build and maintain warships and submarines. The thousands of cubicles were arranged in such dizzying arrays that they had been assigned addresses.

Officers found ways to improvise. They piled furniture in the atrium for cover. One officer took the access card from the body of a slain security guard to get through locked entrances, and remembered to prop open the doors for officers who followed. A Park Police officer, Matthew Cooney, helped a woman who had been wounded get to the roof. She was taken to safety aboard a Park Police helicopter.

“You couldn’t come up with a more complex law enforcement mission than on that day,” said acting Park Police Chief Robert MacLean, who was deputy chief at the time. The officers, he said, “had core values of protecting life before protecting themselves.”

Hiott, who grew up in a small town in North Carolina, came to Washington so his wife could study law. He had a degree in criminal justice and got a job with the Park Police after finding the agency via an Internet search.

For him, the morning of Sept. 16, 2013, began like any other. He had the 6 a.m. to 6 p.m. shift and was assigned to Beat 113, a vast area stretching from the Mall in Northwest through what they call the “pocket parks” of Capitol Hill to the Navy Yard in Southeast. He accompanied colleagues to Ted’s Bulletin on Barracks Row, eating either the biscuits and gravy or the big breakfast sandwich. He can’t recall which.

He drove his cruiser to James Creek Marina, near a collection of federal offices and a Coast Guard Station on Buzzard Point. Callers routinely complain that fishermen park in reserved spaces, and Hiott was checking. He pulled into the parking area just as a call about shots fired at the Navy Yard came over his radio.

The dispatcher initially said, “No assistance needed.”

Hiott assumed it was ceremonial gunfire at the military installation. Police have said the first 911 call came at 8:17 a.m. and 30 seconds, a minute-and-a-half after Alexis’s first shot. It was from a man on the fourth floor who said he heard what sounded like a safe dropping. He looked over his cubicle partition and saw Alexis shoot a woman sitting in her chair. He ducked under his desk, behind a metal filing cabinet, and dialed.

Officers first were called to investigate the “sound of gunshots.” Seconds later, after it was known that someone had been hit, the call was classified as a fatal shooting. That drew an urgent but standard police response to a homicide, without alerting active-shooter teams.

Active-shooter alarm

Unsure of what was happening, Hiott pointed his white Ford Crown Victoria cruiser toward the Navy Yard and got on Potomac Avenue. When he reached South Capitol Street, near Nationals Park, the dispatcher sounded an urgent alarm: “All active-shooter-trained officers please respond to the Navy Yard.” Hiott turned on his lights and siren and jumped in behind a D.C. police car heading to the gated military installation. The Navy Yard had a few armed military police and contract security guards watching over 14,000 workers.

Hiott grabbed his rifle and ran to the command post on M Street SE, where he was grouped with other officers and sent inside. The teams typically consist of three to five officers trained to confront gunmen. Some officers had entered Building 197, but the first organized teams started streaming in at 8:34 a.m., 18 minutes after Alexis fired his first shots.

Hiott said he knew that people had been killed, but he didn’t see bodies as he and others, including a Park Police colleague, Officer Andrew Wong, wound their way upstairs to the third level. He heard gunfire, but an echo made it difficult to know where the shots were coming from.

The police report on the shooting revealed several instances in which officers narrowly missed Alexis. In one case, officers passed an open stairwell on the second floor moments before Alexis reached the top. D.C. Police Chief Cathy L. Lanier called the manhunt an “invisible fight,” saying Alexis could have remained hidden for days in the maze of offices and desks.

At 9:12 a.m., a team of two D.C. officers and two agents with the Naval Criminal Investigative Service made its way to the third-floor cubicles of the amphibious warfare division. About halfway down the hallway, Alexis fired on the group, and Williams was struck.

The NCIS agents — Brian Kelley and Ed Martin — dragged Williams to safety as D.C. Officer Emmanuel Smith provided cover. Hiott had just reached the entrance of the room.

Alexis was there.

“We need to find him and stop him,” Hiott recalled thinking.

Navy Capt. Chris Mercer, his executive assistant and two colleagues were huddled in a corner office. They had heard Alexis walking along the corridor, shooting. They had heard the frantic cries of “Officer down!” when Williams was shot. They listened as the police voices in the hall grew softer, indicating a retreat and dashing hopes of a rescue.

Back at the hall entrance, the police teams broke up amid the chaos. Hiott and DeSantis were with Andrew Wong, the other Park Police officer. Wong stayed at the southern entrance to the room to provide cover, while DeSantis and Hiott moved north up the corridor, toward Alexis.

“We didn’t know if we were going to drive him into a corner and he’d give up or we’d have to take him out,” Hiott said.

Alexis was killed in the cubicle of Mercer’s executive assistant — No. 3W 2851.

He had been inside the building for 69 minutes, going from hunter to hunted, the District’s police chief said. Hiott pronounced the hunt over 51 minutes after the first organized team of officers had gone inside.

Wong helped lead Mercer and the others out while other officers began their search for a possible second gunman, at that time still thought to be on the loose.

Hiott said he has no regrets, but also “no sense of satisfaction.” His job, he said, “is to help people in danger,” and people died. That most of the victims, if not all, were killed before he entered the building is of no comfort. “Maybe if we got there faster,” he said, his voice trailing off.

Hiott said he did what he was trained to do.

“There was a person shooting people and we had to stop it,” he said. “It’s not easy to take someone’s life. It needed to be done. That’s what we did.”

Aaron C. Davis contributed to this report.

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