Neighbor Matt DiPinto of Vernon, Conn., told local reporters that Christopher Krumm made the comments while giving him a ride home a few weeks ago.
"He's like, `So my dad gave me Asperger's ... and my dad should have never had any kids. He should have never had me and passed it on to me, and the government shouldn't have let him have kids,'" DiPinto told Fox affiliate WTIC-TV. "It was just out of nowhere ... but he seemed pretty livid about it."
Police in Casper, Wyo., say Krumm shot an arrow into the head of his father, James Krumm, with a high-powered bow Friday while his father was teaching a computer science class at Casper College.
James Krumm, 56, managed to wrestle with his 25-year-old son and gave time for about six students to flee, an act police called heroic. Authorities say both men died after Christopher Krumm stabbed himself and then his father. Before the classroom attack, police say Christopher Krumm fatally stabbed his father's live-in girlfriend, Heidi Arnold, 42, at the home she shared with James Krumm about two miles from campus.
The motive for the attack isn't clear.
Vernon police searched Christopher Krumm's apartment on Friday night. Officers didn't disclose what they found, but said any items of interest would be turned over to investigators in Wyoming.
Neighbors say Christopher Krumm moved into the apartment building last summer and appeared to work in construction or for a utility, because he wore a neon safety vest, The Hartford Courant reported. They say he was quiet and appeared to be anti-social.
The killings stunned people in the apartment building.
"It's so insane," said Kim Warren, another of Christopher Krumm's neighbors. "You never would have guessed he would have done something like that."
Mickie Goodro, of Twin Falls, Idaho, a friend of James Krumm and Arnold, told the Casper Star-Tribune that Christopher Krumm was in her Calculus class when she taught at Casper College. Krumm graduated from Natrona County High School in Casper in 2005 and studied electrical engineering at Colorado School of Mines, the newspaper reported.
Christopher Krumm's previous addresses include one in the western Massachusetts city of Springfield and others in the Colorado cities of Golden, Fort Collins and Lakewood.
(Copyright 2012 by The Associated Press. All Rights Reserved.)