Nairobi, Kenya — An American businessman has been identified as one of at least 21 people killed in the terror attack on an upmarket hotel complex in Nairobi, plus the five militants killed, according to police. Two people accused of facilitating the attack have been arrested. Some 28 other people were hurt and hospitalized.

Of the civilian victims, 16 were Kenyan, one was British, one was American and three were of African descent, but their nationalities were not yet identified, police said.

Jason Spindler, the director of a business development firm who was based in the Kenyan capital, was killed in Tuesday's attack according to officials in Kenya. His family and friends have also spoken about his death.

Get Breaking News Delivered to Your Inbox

Spindler's friend Chris Schroeder remembered him in a Facebook post as "one of those rare men who was loved by pretty much anyone he touched in Kenya and around the world." Schroeder said Spindler, "chose a life of hope and inclusion. I am grateful to have known and learned from him."

The slain American's family said in posts on social media that he was a survivor of the Sept. 11, 2001, terror attack on the World Trade Center in New York City, where he was living and working at the time.

The U.S. State Department has confirmed that an American citizen was among those killed, but had still not formally released the victim's identity as of Wednesday. CBS News saw at least one U.S. Embassy official at the morgue in Nairobi on Wednesday.

Jason Spindler was one of those rare men who was loved by pretty much anyone be touched in Kenya and around the world. Today he was killed in the terrible al shabab attack in Nairobi. He chose a life of hope and inclusion. I am grateful to have known and learned from him. pic.twitter.com/B4YnxB6bic — Chris Schroeder (@cmschroed) January 16, 2019

Kenya's president said Wednesday that security forces had killed the Islamic extremist gunmen whose assault on the luxury hotel and shopping complex took "innocent lives."

"Go back to work without fear"

"All the terrorists have been eliminated," President Uhuru Kenyatta said in announcing an end to the operation to secure the complex in Nairobi.

In a televised address, Kenyatta didn't say how many attackers were involved. He said more than 700 people were evacuated during the security operation and he urged Kenyans to "go back to work without fear," saying the East African country is safe for citizens and visitors.

Hours before Kenyatta spoke, sporadic gunfire could be heard from the scene after scores of people were rescued at daybreak during what police called a mopping-up exercise.

Al-Shabab — the Somalia-based extremist group that is allied to al Qaeda — claimed responsibility for the carnage at the DusitD2 hotel complex, which includes bars, restaurants, offices and banks and is in Nairobi's well-to-do Westlands neighborhood, frequented by foreigners. Al-Shabab carried out the 2013 attack at the nearby Westgate Mall in Nairobi that killed 67 people.

Authorities sent special forces into the hotel to flush out the gunmen. Early Wednesday, Kenya's Interior Ministry said in a tweet that all buildings had been secured and there was no further threat. At dawn, another explosion and gunfire were heard.

Inside the hotel terror attack

"To God be the Glory. We have been rescued. Over 50 people in my group. No injuries," tweeted a Kenyan businesswoman, Aggie Asiimwe Konde.

Describing the ordeal, Lucy Wanjiru said she had been trying to flee when she saw a woman on the ground floor get shot. Wanjiru ended up in a washroom with several other scared people. Her friend Cynthia Kibe stayed in contact with her by phone overnight.

"I think I panicked when she told me that the gunshots are next to her," Kibe said. "I had to keep telling her 'Just wait, help is on the way, they are almost there, they are almost there.' And then at one point she was like, 'Please tell me I am getting out of here alive' and then it was just like my breaking point."

Kenya's Citizen TV aired security-camera footage that showed at least four heavily armed men in dark-colored, paramilitary-style gear.

The coordinated assault began with an explosion that targeted three vehicles outside a bank, and a suicide bombing in the hotel lobby that severely wounded a number of guests, said Kenya's national police chief, Joseph Boinnet.

Kenyan hospitals appealed for blood donations even as the number of wounded remained unclear.

Associated Press video from inside the hotel showed Kenyan security officers searching the building and scared workers emerging from hiding while gunfire could still be heard. Some climbed out a window by ladder. One man got up from the floor where he appeared to be trying to hide under a piece of wood paneling, then showed his ID.

A man who gave the AP only his first name, Davis, described how he had escaped with colleagues by fleeing down a fire escape.

"It's a traumatic experience. It shakes you," he said. Still, Davis said he was impressed by the "inner strength" and compassion of people who helped each other in the midst of danger.

His own thoughts, he said, were: "Get people out and get out yourself. That's it."

U.S. airstrikes not stopping al-Shabab

Like the attack at the Westgate Mall, this one appeared aimed at wealthy Kenyans and foreigners. It came a day after a magistrate ruled that three men must stand trial in connection with the Westgate Mall siege.

Al-Shabab has vowed retribution against Kenya for sending troops to Somalia to fight it since 2011. Tuesday's violence came three years to the day after al-Shabab extremists attacked a Kenyan military base in Somalia, killing scores of people.

The group has killed hundreds of people in Kenya. In the deadliest attack, al-Shabab claimed responsibility for an assault on Kenya's Garissa University in 2015 that killed 147 people, mostly students.

The latest carnage demonstrated al-Shabab's continued ability to carry out spectacular acts of bloodshed despite a dramatic increase in U.S. airstrikes against it under President Trump.