"David was a patriot. David was a warrior when he needed to be, and also a peacemaker," James Berry said about his son.
"He was intelligent and resourceful. He would not break down in a fight when liberty, freedom and justice was at stake. I lost a son yesterday, but I believe in what David did, and I stand proud of him while I privately mourn," he told CNN's "The Lead with Jake Tapper" on Wednesday.
The Libyan branch of ISIS has claimed responsibility for the gun and bomb attack that killed five foreigners, including Berry, an American security contractor.
Five Libyans also died in Tuesday's attack on the Corinthia Hotel, said a spokesman for a security division of the Ministry of Interior in Tripoli, Essam al-Naas.
Two attackers were killed, he said, saying it appeared they were Libyans.
The five-star hotel is known as one where foreigners and government officials stay and meet to conduct business.
The Libyan branch of ISIS released photos of the two gunmen it said had carried out the attacks, identifying them as Abu Ibraheem Al-Tunsi and Abu Sulaiman Al-Sudani. Their naming convention indicates that the men were of Tunisian and Sudanese origin, respectively.
The FBI is expected to open an investigation into the incident, two U.S. officials told CNN.
According to military records, Berry was in the U.S. Marine Corps, completing six deployments in Afghanistan, Kuwait and Iraq. He retired in September 2012, after a dozen years of service.
He was working for Crucible, a security firm.
According to its website, the Virginia-based firm "provides high-risk environment training and global security solutions to employees of the U.S. government, NGOs, and multinational corporations who live and work in dangerous and austere locations worldwide."
His father said Berry was fluent in Arabic and knew his way around the Arab world.
"He knew how to approach Arabic people on a foreign shore and not ... discriminate against them -- not come across as, 'I'm am American warrior and I'm going to do it this way.' He was very conciliatory in nature," James Berry said.
His son leaves behind a wife and four children.
The other foreigners killed in the attack were a French citizen and three people from Tajikistan, al-Naas said.
The French Foreign Ministry confirmed that a French citizen was among the dead but did not identify the victim.
The Tripoli government, which is not internationally recognized, said the intended target of the attack was its prime minister, Omar al-Hassi, but the claim has not been confirmed.
Al-Naas said that at least two Libyan security personnel were killed in the attack.
An online group that supports ISIS said the attack was carried out in the name of Abu Anas al-Libi. He was an alleged al Qaeda operative accused of involvement in the bombing of U.S. embassies in Africa. He was captured by U.S. special forces in Tripoli in 2013. He died in a U.S. hospital this month.
It's this declared link to al-Libi's capture by the United States that has prompted the FBI to investigate.
Fighters loyal to ISIS have for several months been in control of the Mediterranean port city of Derna
in eastern Libya, near the border with Egypt. They are suspected in other attacks elsewhere in Libya, including in Tobruk, Al-Bayda and Tripoli.
Explosion then gunshots
Tuesday's attack began when militants detonated a car bomb in the parking lot of the hotel. The gunmen then shot their way into the hotel.
The high-rise hotel is popular among government officials, some of whom live there.
Until now, it was seen as one of the remaining secure locations in Tripoli for diplomatic and government activity.
The attack, different in scale and coordination to those seen previously -- even after months of violence in Libya's east -- sends the message that nowhere in the country, or its capital, is safe.
Authorities say they are now in control of the hotel premises and are starting their investigation.
Threats against U.S. citizens
The self-proclaimed Tripoli government, formed by a coalition of militias, holds sway only over the capital and surrounding areas. The internationally recognized parliament was forced to leave the capital after militia groups seized control of the city in the summer.
The U.S. Embassy in Tripoli, the United Nations and other international organizations and businesses also evacuated their staffs from Tripoli in the summer due to the unrest.
The U.S. State Department last week issued a warning advising U.S. citizens against all travel to Libya and recommending that any U.S. citizens currently in the North African country should leave immediately.
"Extremist groups in Libya have made several specific threats against U.S. government officials, citizens, and interests in Libya," it said.
"Because of the presumption that foreigners, especially U.S. citizens, in Libya may be associated with the U.S. government or U.S. Non-governmental organizations (NGOs), travelers should be aware that they may be targeted for kidnapping, violent attacks, or death."