Greg Owen shot a six-under 66, James Love had a five-under 67 and Fran Quinn carded a 4-under 68 -- all among the 27 players who broke par at the toughest course on the Nationwide Tour schedule.
Omar Uresti won at Wente Vineyards last season with an even par total after 72 holes -- one of just two players in the developmental tour's history to win with a score of even par or worse.
Thursday, Killeen tied the course record in just his sixth Nationwide Tour start.
He birdied every other hole on the front nine and posted eight birdies in all through 17 holes before making his only bogey of the round at the par-4 18th hole.
Killeen knocked his last approach shot into a greenside bunker and walked off with a five.
Despite the bogey finish, Killeen bested his previous low score on the Nationwide Tour by three shots. The round was highlighted by a 20-foot birdie putt at the first hole and birdie putts of 40 and 30 feet later on.
'I kept it in play and that's important on this course,' Killeen said. 'I was really relaxed out there. I haven't been playing bad this year, it's just a matter of getting used to everything. It's a matter of getting comfortable, that's all.'
Killeen, 26, tied Jason Dufner's course record from 2006. The scoring average was more than two shots above par at 74.322 strokes.
'I missed a couple of greens but it wasn't by much so I never really had to bear down on a lot of tough par putts,' said Killeen. 'I knew this course was hard but I tried to keep it in play off the tee and I hit my irons great.'
Only one player in the 144-man field -- Aron Price, who shot a 70 -- made it through the round without a bogey.
At the end of the day, one golfer had presumably had enough -- three-time Nationwide Tour winner Franklin Langham, who withdrew after shooting an 11- over 83.
Langham was one of 11 players who posted rounds in the 80s on Thursday.