James Usera played football with Dorner at Southern Utah University in the late 1990s and they became friends off the field.
"Just absolute befuddlement and shock when I learned about it this morning, and trying to piece things together and in being asked questions about what I know about Mr. Dorner, my experiences with him, and I try and think, was there any indication of this and, you know, there just isn't," said Usera.
Usera told the Los Angeles Times that the two had friendly debates about the extent of racism in the U.S. and take trips into the Utah desert to hunt rabbits.
"He was a typical guy. I liked him an awful lot," said Usera, who's now an attorney in Salem, Ore. "Nothing about him struck me as violent or irrational in any way. He was opinionated, but always seemed level-headed."
Dorner, who was a running back for the football team, graduated in 2001 from the Utah school, where he majored in political science. The 33-year-old former LAPD officer and Navy reservist is wanted in connection with the shootings of three police officers in the Inland Empire and a double murder in Irvine.
A massive manhunt is still under way for Dorner. Investigators are focusing their search efforts in the Big Bear area, where Dorner's burned-out unoccupied truck was found Thursday afternoon.
The Associated Press contributed to this report.