After Kirk hooked his tee shot at No. 18 into the left rough, he hit his approach from 155 yards over the green. A nice chip set up the winning putt.
Snedeker, who closed with a 67, hit a similar tee shot as Kirk on the final hole and hit to 12 feet. But his birdie try that would have tied Kirk slid left of the hole.
Bohn had a 63 that included six consecutive birdies on the front nine. Spieth shot 65, with a near-birdie that became a bogey at the par-3 16th hole.
Colin Montgomerie wins Senior PGA Championship
Colin Montgomerie answered two front-nine challenges with birdies, then pulled away, shooting a 3-under 69 on Sunday to win the Senior PGA Championship by four strokes.
Montgomerie finished at 8-under 280 on The Pete Dye Course at French Lick Resort to successfully defend his title and win for the third time in the last six senior major championships. The 51-year-old Scot won last year at Harbor Shores in Michigan, and also won the U.S. Senior Open in July in Oklahoma.
Montgomerie earned $495,000 and he made it look easy.
Esteban Toledo twice pulled within a shot on the front nine, but couldn't keep up. Toledo shot a 69 to finish second. Woody Austin was another shot back after a 69, and Brian Henninger and Scott Verplank tied for fourth at 2 under. They each shot 71.
Montgomerie and Bernhard Langer have won four of the past five senior majors, with Jeff Maggert's win last week in Alabama in the Regions Tradition the lone exception.
Playing in the final twosome with Montgomerie. Langer had a 74 to finish sixth at even par.
Byeong Hun An sets tournament record in BMW PGA Championship win
Byeong Hun An shot a 7-under 65 to win the BMW PGA Championship at Wentworth with a tournament record total of 21 under.
The 23-year-old An captured his first European Tour victory after Francesco Molinari, who had at least a share of the lead for the first three rounds, only managed a 74. He finished fifth, nine shots back.