Kumar shot a final-round 4-under 68 to win the Palo Verde Amateur at Whirlwind Golf Club's Cattail Course on Wednesday.
Hagstrom had pulled even with Kumar several times during the day and was only two back heading to the 18th hole but a bogey led to the final three-shot margin.
Cade Anderson (Scottsdale, Ariz.), who plays collegiately at Rutgers, finished third four strokes behind Hagstrom.
"This win means a lot to me because it gets my name out there to coaches," said Kumar. "I am currently in the transfer portal and I want to continue my college career at a competitive program. I’ve been hitting the ball really well the past few weeks and it really paid off during the tournament. I’ve (also) worked a lot on my putting and the last few months and I’m finally starting to see that pay off under pressure.”
The Palo Verde is the second tournament in the 2022-23 Troon Saguaro Amateur Series, of which there are 12 scheduled events. The next event will be the Silver State Amateur at Paiute Golf Club in Las Vegas, June 5-8.