Lanny Berman, executive director of the American Association of Suicidology, told ABCNews.com that the suicide of a 10-year-old is "very rare" and usually doesn't happen without clear warning signs, such as "very serious symptoms of aggression ... or just being out of control in some other ways."
"Suicide at this age is very impulsive," he said.
And if Aquan had indeed threatened suicide to a school employee, it should have been taken seriously no matter how flippant it may have sounded, Berman said.
"We always advise to take every threat seriously," he said. "If you're wrong, big deal. If you're right you may save a life."
Evanston Police Commander Tom Guenther told ABCNews.com today that his office was aware of the medical examiner's ruling, but would not draw its own conclusion until the investigation is complete.
Police are continuing to talk to a wide swath of people, including students, parents and school employees.
He declined to say whether foul play was being considered and said it would be "inappropriate" to comment on whether police have had previous dealings with the family.
A public records search showed Angel Marshall pleaded no contest to cocaine possession in 2003 and was sentenced to community service in 1999 on a handgun charge.
Lallie Marshall said her great-grandson loved his video games and his time playing sports. He'd been playing on football and basketball teams for about two years.
Marshall said Aquan's older brother Adam told her that Aquan wanted to be an NBA star when he was older.
"He was a nice little boy," she said.
The Evanston/Skokie School District 65 posted a message to parents and the community on its Web site Wednesday mourning the loss of "an Oakton School fifth grader" and saying that counselors, staff and psychologists would be made available to students.
"It is important for us to let you know that at this point in the investigation, it appears this is an isolated incident involving one student," the message read. "No other students were in harm's way."
"If there is someone to blame, I have to take the blame for that because I'm the superintendent of schools," Superintendent Hardy Murphy told an ABC affiliate.
Few who knew Aquan wanted to talk about him or his death today. Though one member of the Oakton Elementary School PTA expressed sadness over the incident, no one would comment further.
Aquan's football coach Tracey Wallace was quoted by the Chicago Tribune as saying he had potential "not only as a citizen, but as an athlete."
But when contacted by ABCNews.com today, Craig Thompson, executive director of Evanston Jr. Wildkit Football, said he had been advised by the club's attorney not to comment in light of possible forthcoming litigation against the school district.