Dejounte Murray scored 21 points and Bogdan Bogdanovic added 20 for the Hawks, who snapped a two-game losing streak.
Williams stole the ball from Young and dunked to cut Atlanta’s lead to 133-132 with 15.3 seconds left. Atlanta's John Collins was fouled with 14.5 seconds remaining. He made both free throws to make it 135-132.
Gilgeous-Alexander drove to the hoop to try to get quick points, but Murray blocked his shot. Gilgeous-Alexander rebounded and missed again, and Murray came up with the ball. Murray was fouled and made two free throws at the other end with 2.7 seconds remaining to put the game out of reach.
The teams were tied at 77 at halftime. It was the most points the Hawks have scored in a half this season. Gilgeous-Alexander scored 26 points and Young had 22 before the break. Atlanta shot 58.3% from the field in the first half, while Oklahoma City shot 56.9%.
Atlanta led 109-104 at the end of the third quarter, then scored the first 10 points of the fourth. Oklahoma City responded with a 9-0 run to trim its deficit to six and force Atlanta to call a timeout. The game was close the rest of the way.
Hawks: F De'Andre Hunter sat out with asthma symptoms. ... Murray was called for a technical foul in the second quarter. ... Young was called for a technical in the third. ... Collins had 19 points and 10 rebounds. ... Capela had 18 points and 10 rebounds.
Thunder: G Tre Mann stole an inbounds pass, elevated, cocked the ball back and unleashed a towering right-handed jam in the final minute of the first quarter. ... G Josh Giddey had 16 points, eight rebounds and six assists.
Hawks: Host the Los Angeles Clippers on Saturday.
Thunder: Host the Cleveland Cavaliers on Friday.
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Cliff Brunt, The Associated Press