He was convicted of supplying guns to the two men who opened fire outside the Prophet Mohammed cartoon drawing contest.
The gunmen, Elton Simpson and Nadir Soofi, were killed by police, prompting some Islamophobes to react with glee.
A security guard was shot in the leg before the men were killed. The gunmen carried three pistols, three rifles, and more than 1000 rounds of ammunition.
Kareem will be sentenced on June 27 and could face up to 45 years.
He denies knowledge of what his friends were planning.
Prosecutors argue Kareem hosted Simpson and Soofi at his home, where they planned the attack, and went for shooting practice in the Arizona desert.