Germanie Alexander and BreAnna Holmes were on their way to work on Thursday, July 2 when they were stopped by police and told to evacuate the scene because of a report of possible gun shots fired inside the Washington Navy Yard. (McKenna Ewen and Whitney Leaming/The Washington Post)

The police response to Thursday’s unfounded fears of a gunman at the Washington Navy Yard appeared more streamlined and less confusing than in 2013, when a lone gunman killed 12 people and officers sent to confront him were met with an array of obstacles, according to initial assessments by law enforcement authorities.

Unlike two years ago, when police encountered locked gates at the installation in their search for Aaron Alexis, law enforcement officers on Thursday quickly got through and into the secure Naval Sea Systems Command headquarters where naval engineers buy, design and maintain warships and submarines.

D.C. Police Chief Cathy L. Lanier said that within 20 minutes of the first call, she was sitting next to a Navy vice admiral in a command center, and authorities were accessing live video feeds. In 2013, she said the Navy didn’t tell her the video existed, preventing police from tracking Alexis as he stalked workers and roamed the maze-like 600,000-square-foot building for 69 minutes.

“It appears that all the things that we tried to correct and make go better from the last incident went very, very well,” Lanier told reporters. She added she was “very happy that this turns out to be a great exercise for us to see if we fixed what we needed to fix, and nobody is hurt.”

Comparisons between the two incidents are difficult both because the authorities have yet to write and compile reports and because there wasn’t gunfire Thursday. There was some initial chaos and worrisome reports — a suspicious person on a roof, another leaping a fence — but police said they believe that authorities and witnesses mistook fleeing workers or plainclothes police officers for possible gunmen. But overall, Thursday’s scene lacked the intensity and energy that came amid the mass killing in 2013.

After that shooting spree, D.C. police compiled an 82-page report dissecting the response to Alexis’s rampage. While the report commended officers who it said acted heroically, including the two who were shot during exchanges with the killer, it criticized some command decisions and the abilities of different law enforcement agencies to work together.

For example, several agencies sent their own command buses and set up communications lines with their officers, confusing those on the ground about who was in charge. In addition, ­Lanier complained, “We never saw the base commander during the entire incident.”

Lanier said Thursday that within 20 minutes of the initial call about gunshots, she was next to Vice Adm. William H. ­Hilarides, commander of the ­Naval Sea Systems Command, and FBI agents and others were able to “access everything we needed in terms of cameras inside of the building.”

In a later interview after a two-hour internal briefing, ­Lanier said her officers and those from other agencies followed new training that came after the report on the 2013 incident. She said a red “hot phone” got her in touch immediately with other chiefs, and officers followed protocols even after it was apparent there had been no shooting.

Delroy Burton, the chairman of the D.C. police labor union, listened to officers talking over their radios as the incident unfolded, and he said that “it sounded well organized. It sounded as if we’ve learned some valuable lessons.” He said some other agencies did have trouble with their radios working in the confines of the building, but he said the digital radios D.C. police used seemed to work fine.

Jim Konczos, chairman of the U.S. Capitol Police Labor Committee, said the law enforcement response to the Navy Yard incident Thursday was “very different” from 2013.

Two years ago, Konczos said, the Capitol Police’s SWAT team arrived at the scene only to be told by supervisors over the radio and on their Blackberrys to return to the Capitol.

Capitol Police disputed that version, saying that some of its officers had gone on their own to the Navy Yard and were sent back to protect other institutions.

Konczos said that on Thursday there was no confusion. He said the SWAT team and other Capitol Police officers arrived and were put to work. “Hopefully, Capitol Police kind of learned their lesson as far as what we should be doing, and today will be the norm going forward,” he said.

Konczos said that different law enforcement agencies seemed to coordinate more seamlessly. He said Thursday’s response “would be exactly what the public wants. . . . I can only imagine how employees feel today, being evacuated just two years after it happened, but from the law enforcement perspective, it’s a good trial run.”

There are still several recommendations from 2013 that have not yet been fully implemented or are too early to evaluate.

After 2013, police complained that their AR-15 assault rifles were too long to maneuver in the cluttered confines of a ­warehouse-size office building filled with cubicles. Lanier also wanted earpieces for police radios after one of the wounded officers believed a transmission alerted Alexis to his position.

Lanier said 500 M-4 rifles were purchased and distributed to newly trained officers, along with 4,000 earpieces. The new rifles, along with AR-15s, were used Thursday.

Also, Building 197 was rebuilt from the inside after the massacre, but Lanier said the floor plan and complex numbering system in which aisles and desks had addresses remained the same. She said it follows a standard military numbering system, something officers were unfamiliar with in 2013 but now know. “Our people knew the layout,” Lanier said.

D.C. Mayor Muriel E. Bowser (D) said “we know that there have been a lot of lessons learned from [the] previous incident.” Authorities said the response to Thursday’s incident will be reviewed and protocols further refined if necessary.

Navy Vice Adm. Dixon Smith called the response from D.C. police “outstanding this morning and very much appreciated.” He added, “We’re going to review this again to see what went right and what we can continue to improve upon on.”

Police weren’t the only ones to refine their tactics since 2013. Workers are now allowed to take their cellphones inside the building, for example; that practice had been barred for security reasons.

Barry Plunkett, 60, the special counsel for litigation in the ­Naval litigation office, said the Pentagon ordered him to account for his staff of roughly 40 people. He now had access to the roster electronically, and he was able to e-mail and account for everyone quickly.

Plunkett, who is from Ellicott City, said about 10 people were inside Building 36. He said those people told him they had gathered around a station in the office equipped with water, food and even portable toilets — a consequence, he said, of the 2013 incident.

“We learned some stuff from the last time around,” he said.

Arelis Hernandez, J. Freedom du Lac, DeNeen L. Brown, Abigail Hauslohner, Joe Heim, Aaron C. Davis, Clarence Williams and Julie Zauzmer contributed to this report.