Discovery Communications execs held a town hall meeting with staffers on Thursday (above), one day after a lone gunman took three employees hostage at the company’s headquarters.

James Lee, 43, was killed by police after a four-hour standoff; no one else was injured.

“I keep thinking of three words since the situation ended: ‘All are safe,'” Discovery CEO David Zaslav told employees, who returned to Discovery’s Silver Spring, Md., headquarters on Thursday.

Discovery re-opened the building on Thursday at 10 a.m. in order to allow staffers to retrieve their belongings, and also to hold the meeting with Discovery brass.

According to Discovery spokeswoman Michelle Russo, counselors were on hand to talk to employees and will remain on campus next week. Hotlines will also be available to affected staffers over the weekend, and counselors have been dispatched to the homes of the three Discovery employees who were held hostage.

LeeprotestAdditionally, Discovery employees were told to go home after 1 p.m. on Thursday. Discovery also decided to close its headquarters on Friday, giving staffers a chance to spend extra time with their families and kick off the holiday weekend early.

Decision to close the building on Friday also comes as police continues to command the Discovery lobby, where the hostage crisis took place. That area, which includes the Discovery public entrance, remains off-limits to everyone but authorities, who were still investigating the incident.

Moving forward, Discovery plans to add additional security to its headquarters, Russo said.

“Certainly it’s not because we think there’s an additional threat, but we want our employees to feel safe,” Russo said. “All our systems worked yesterday… it could have been a different outcome. We’re very lucky.”

Russo confirmed that Discovery execs and security employees were very familiar with James Lee, the man that police said walked into Discovery HQ on Wednesday afternoon holding a gun and wearing explosives on his body. Lee had been arrested outside Discovery in 2008 for disturbing the peace.

“A whole dossier about him was at security,” Russo said. “We knew quickly who was at the building. We had a restraining order against him, he couldn’t approach within 500 feet (of us).”

That order, officials confirmed yesterday, had expired just two weeks ago.

Russo lauded Discovery staffers for calmly leaving the building.

“They followed instruction and did what they were told to do,” she said. “It all unfolded pretty quickly.”

Discovery Russo said Discovery did not document the events themselves, and had no plans to do a story on one of its channels (which would include Investigation Discovery).

Discovery didn’t release the names of the hostages, although one staffer, Jim McNulty, left a note of thanks on a Discovery blog:

First of all, I want to thank the Montgomery County Police and all the agencies that responded today for helping to ensure the safety of all my colleagues at Discovery Communications.

And for helping to get me and my fellow hostages out safely.

I want to thank my family, friends and coworkers for their thoughts and prayers during this situation.
And I especially want to thank Discovery for their support.

At this time, because the criminal investigation is still ongoing, I will have no further comments regarding the events of this afternoon.

But I thank you for all for your concern during these harrowing hours.

About 1,900 people work at the Discovery headquarters, although it was unclear how many employees were there on Wednesday. Lee also approached the building during lunch hours, when many staffers were out of the building.

Read our liveblogging of the Discovery crisis as events unfolded yesterday here.