He was a basketball-loving kid from the Midwest who turned into a jihadi fighting for terrorists in Syria.
Exactly what spurred Douglas McAuthur McCain's metamorphosis remains murky. But while his radicalization and death have stunned loved ones back home, his actions abroad have raised fears that other Americans may follow suit.
Here's what we know about the 33-year-old man who died while fighting for ISIS, the radical militant group that has captured swaths of Iraq and Syria and spawned major concerns in the United States:
He grew up in Minnesota
McCain grew up in the Minneapolis suburb of New Hope, his friend Isaac Chase said.
The two lived in the same New Hope apartment building and became fast friends.
"When I first moved here, I didn't know anyone, so I went to the park and I would see him and his brother and a bunch of other people playing basketball, and he asked me if I wanted to play," Chase said.
"We just hung out pretty much from 10 o'clock in the morning all the way until nighttime. We'd just play basketball and talk. ... He was an older guy that I looked up to. He was actually a good dude."
Chase described McCain as a nice, quiet young man, but one who was looking for purpose in life.
When Chase joined the Air Force in 2007 and served in Iraq, McCain was impressed that his friend was making something of his life and wanted to do the same, Chase said.
But after learning that McCain died while fighting for ISIS, which is trying to rule an Islamic state across Iraq and Syria, his friend was bewildered.
"It just hurts a little bit knowing that if he was over there and I was over there at the same time, we would've been going against each other," Chase said. "That's what hurts the most because he was a good person, and I just don't understand why anyone would do anything to the U.S."
His family is stunned, too
McCain's transformation to a jihadi left his family "devastated" and "just as surprised as the country," said his uncle Ken McCain, who lives in Minnesota.
Chase described McCain's mother and father as good parents. He said the mother attended church regularly, and the father is deceased.
McCain converted from Christianity to Islam several years ago, his uncle said.
He described the nephew he knew as "a good person, loved his family, loved his mother, loved his faith" -- the latter being a reference to the Christianity he practiced before his conversion.
The family wasn't alarmed by his conversion. But McCain's Facebook posts sympathetic to ISIS got relatives' attention, the uncle said.
He said they last heard from McCain several months ago, when he said he was traveling to Turkey.
His cousin insists he's not a terrorist
McCain's cousin Kenyata McCain said she can't believe allegations that her cousin is linked to a terrorist group.
"We're from Chicago. We grew up in Minnesota. He's not a terrorist -- that's crazy," she told CNN affiliate KARE.
"His religion was very important to him, but those people -- the ISIS people -- they don't represent what my cousin's beliefs are or were at all."
Kenyata McCain wondered if her cousin may have gotten caught up in the wrong crowd.
"Why was he in Syria? ... What kind of people was he hanging around? I feel like maybe it was the people he was hanging out with because that's not who he is. He's not ISIS," she said.
He had run-ins with the law back home
McCain had been arrested several times in Minnesota since 2000, according to the Hennepin County Sheriff's Office.
The alleged offenses included disorderly conduct, speeding, driving after revocation, theft by swindle and giving an officer false information.
The U.S. government had been monitoring him
McCain is the first American known to have been killed while fighting for ISIS.
U.S. counterterrorism investigators had been looking into his activities for some time before his death, a U.S. official said.
The official said McCain was on a list of Americans who are believed to have joined militant groups and who would be stopped and subjected to additional scrutiny if he traveled.
Chase said he can't understand how McCain could have joined terrorist ranks.
"It don't make no sense. The Doug I know is a good person, and I wouldn't even think that he would do anything like that."