Gurpreet failed to make the final of men's 25m Rapid Fire Pistol after finishing seventh in the qualification round, while Mairaj ended ninth after losing in a shoot-off in the Men's Skeet event.
As a rule, the top six are entitled to advance to the finals in both the events.
Gurpreet, who was placed 10th at the end of first qualifying phase with 289 points, collected a total of 292 points for a total of 581, including 24x, to miss the finals by a whisker. His one bad round of 90 yesterday cost him a place in the final of the event.
The 40-year-old Mairaj, who had bagged a historical quota in skeet by winning the World Cup silver at the same venue in April, came very close to qualifying when five were tied with 121.
Also Read
But Mairaj and Anthony Terras became the first to be eliminated, missing the target after three shots at the Olympic Shooting Range in Deodoro.
Having bagged one gold, two silver and one bronze since Athens 2004, shooting now is in danger of returning empty-handed as only Gagan Narang and Chain Singh are in contention on the concluding day tomorrow at the 50M Rifle 3 Position event.
"Skeet is unknown in India. We are not even closer to the world champion. We decided to put India on the map. Skeet was always more challenging and fascinating for me," Mairaj, who is coached by 1996 Atlanta gold medal winner Ennio Falco, said.
"He gave us the belief. I'm really very sad that I failed to put the country's flag on the podium. But it's the journey and not the destination. It comes once in four years, it was not normal."
"We worked very hard. I'm out since April 4, only two days for Eid and went back to Italy. We are well supported. We have produced some results."
On his shoot-off, he said: "I overcame and finished 121, but shoot-off is like a draw. The target goes down, unlike other shooters. Maybe next time, God willing I will do well."
Mairaj said he's already looking ahead to Tokyo 2020.
Mairaj has spent two years with the Italian coach, and Falco said: "We have to begin to work for the next season. We have the World Cup in Rome. We have to respect his performance. He trained very hard and he's a professional."
"First time we qualified, we reached seventh place. The Olympic Games is different experience. The youngsters are coming up. We have to now think of developing Indian team.