Kris Cox and Vance Veazey share third place at 12-under-par 204. Brandt Snedeker, Steve Pleis and 36-hole leader Jeff Brehaut followed at 11-under-par 205.
Hietala rocketed out of the gate with a birdie on the first hole at Le Triomphe Golf & Country Club. He found trouble with a bogey at the par-3 third but responded in style with an eagle at the par-5 fifth.
'I was nervous this morning and I had butterflies all day,' said Hietala. 'The birdie on No. 1 settled me down and then I bogeyed No. 3. But the rest of the day was a whole lot of fun.'
Hietala tallied back-to-back birdies from the par-5 seventh and collected a birdie at the par-4 10th to climb to 12 under. He then birdied the par-5 12th and kept on rolling with a birdie at the par-5 14th.
The 31-year-old made it two in a row with a birdie at the par-4 15th, but he gave that shot back with a bogey at the following hole. Hietala then parred his way in to secure a slim advantage in search of his first career victory on the Nationwide Tour.
'A 65 is in the books and today is over and done with,' said Hietala, who resides in Lafayette, Louisiana. 'I couldn't have asked for a better day.'
Johnson picked up a birdie at the first, but he stumbled to a bogey at the par-four fourth. The Swede countered with birdies on each of his next four holes to make the turn at 11-under.
The 28-year-old added back-to-back birdies starting at the par-4 15th for a round of 66.
Sean O'Hair shot a 5-under 67 that featured an ace at the par-3 sixth. O'Hair was joined by Dicky Pride at 10-under-par 206.
Jason Schultz, Wes Short, Jr., Tim O'Neal and 2002 U.S. Amateur champion Ricky Barnes are knotted at 9-under-par 207.