Scott Hamann of South Portland arrived in Maine late Friday night, five days after the flotilla was intercepted by Israeli troops, resulting in the deaths of nine pro-Palestinian activists.
In a phone interview with The Associated Press, Hamann said troops that landed on the boat he was on fired high-powered paintball guns and threw a "stun grenade" that hit him on the foot before exploding behind him.
People aboard the flotilla expected a confrontation, but not a deadly one, he said.
"As soon as we heard the real guns going off, that's when we knew things were different than what we thought they'd be," he said. "We knew they'd use excessive force, but it was a game changer when we heard they were shooting people."
The six-ship flotilla was attempting to deliver supplies to Gaza in defiance of a 3-year-old Israeli blockade that has aimed to prevent the smuggling of weapons into Gaza that could be used to attack Israel. At the same time, it has deepened the poverty of the 1.5 million Palestinians in the strip and heightened Mideast tensions.
The flotilla's journey ended when Israeli commandos boarded the vessels early Monday morning and clashed with passengers on one ship in a confrontation that left nine people dead.
Israel says troops used force only after they were attacked with weapons. Activists say Israel fired first.
Hamann, 29, owns Harbor Light Films video production company in South Portland. He was documenting the event as a job but also felt strongly about the cause.
David Rubinson, a former music producer in the U.S. who now lives in Eze, France, said he hired Hamann to ride aboard one of the six vessels in the flotilla, shoot video and photographs and post them on the website http://www.witnessgaza.com.
Hamann said the flotilla was in international waters when it was intercepted by Israeli troops. When they boarded his vessel, Challenger I, they destroyed all video footage and camera memory cards, he said.
He and hundreds of others on the flotilla were then brought to an Israeli prison and detained before they were deported.
There, Israeli troops and intelligence officers intimidated and threatened the prisoners, he said. After being brought to an airport to be put on a plane, two deportees were attacked by soldiers when they refused to sign deportation orders, he said.
One of them, he said, was an American citizen who was beaten and bloodied. When soldiers gave him water to wash his face, he refused to do so, saying he wanted people to see what they did to him, Hamann said.
"Then they beat him up really bad and we haven't seen him since. The status, the last I heard, isn't good," he said.
Speaking from France earlier this week, Rubinson said little media attention was paid to another aid flotilla last year that was disrupted by Israel as it made its way to Gaza. This time, he wanted to make sure people worldwide could witness the journey through video and photographs posted on the website.
Rubinson is Jewish, but no longer practices his faith because of his disapproval of Israel's actions against Gaza.
"I'm doing this because it's my people who are perpetrating this tragedy," he said. "I feel it is imperative we do something to stop it."