The surprising Washington Bullets earned the split they wanted in the first two playoff games in Boston tonight when Frank Johnson made a 28-foot, three-point shot with three seconds to play to provide the difference in a stunning 103-102 upset.

"It was my choice and I was going for it," Johnson said after his brilliant 26-point performance. "Coach said to take the three-pointer if it was there and if it wasn't, just try to get two."

Coach Gene Shue had every reason to go for broke on the Bullets' last play, because Greg Ballard had fouled out and Rick Mahorn and Spencer Haywood were playing with five infractions. The Bullets could have wound up very short of rebounders if the game had gone into overtime.

"Frank knew when he left the huddle, he was going for three," Shue said, with an ear-to-ear grin. "This was his night. There was no doubt. Confidence means a lot, and Frank had tremendous confidence."

Johnson had every reason to be confident after scoring 10 of his team's previous 19 points, as the Bullets overcame a 90-84 deficit in the final 5:16. He ended up making 11 of 19, went three-of-three at the free throw line and had eight assists.

This best-of-seven series now is tied at 1, with the next two games set for Capital Centre Saturday and Sunday afternoons. The fifth game will be here Wednesday. If necessary--and it certainly seems likely now--the sixth game will be May 7 at Landover.

"Game 3 will be more of the same, only I think we'll play even better defense," Shue said. "But the Celtics probably will, too, and the scores will keep getting lower."

Shue said the last play was designed for Johnson, and the only question was whether the first-round draft choice from Wake Forest would take a three-pointer or go for the tie.

"We brought two players out to set picks (Jeff Ruland and Mahorn), and Frank had the option to go whatever way he could to get open," the coach explained. "I think we all wanted him to go for the win."

Boston Coach Bill Fitch countered at the timeout by substituting M.L. Carr and Danny Ainge for Larry Bird and Nate Archibald at guards. Ainge, who hadn't played until then, was assigned to Johnson.

"I put Danny in because he's the best defender, one on one," Fitch said. "He's got the size and the speed. You can't blame the guy guarding the man who shot, you've got to look at who was guarding the guys who set the picks."

Ruland set the first screen and Robert Parish jumped off, forcing Johnson to go right. When Mahorn set the second screen, nobody popped out and Johnson was free.

"I thought they'd go for the three-pointer," Fitch said. "They had everything to gain and nothing to lose. I thought we had a better percentage shot than they did, but theirs went in and ours didn't."

The Celtics immediately called time after Johnson shot and set up a play. Bird inbounded the ball to Carr, who got an open jumper to the right of the foul circle. It hit the back rim and the Bullets raced off the court, whooping as if they had won the championship.

This was the first time the Bullets had won here since March 9, 1980, when John (Supe) Williamson led a 133-128 overtime triumph. Boston had won seven in a row over the Bullets.

It looked like another in a series of near misses against the Celtics when the Bullets let an 84-80 lead slip away midway through the fourth quarter.

After Johnson's two driving shots broke an 80-80 tie, the Celtics called time and got down to business. They put together a 10-point rally, with five different players scoring, to take a 90-84 advantage with 5:16 remaining.

Following two free throws by Haywood, who shared scoring honors with Johnson with 26 points, Johnson made a 16-foot fadeaway and a short leaner in the lane to bring the Bullets within one, 91-90.

Parish sank a fadeaway after getting an offensive rebound, then added two free throws with 3:34 left to put the Celtics in front, 95-90.

Pressure foul-shooting kept the Bullets close down the stretch. They didn't miss a free throw in the fourth quarter and scored their last 10 points from the foul line before Johnson's winner.

Ruland (19 points) made four in a row to bring the Bullets within two, 100-98, with 1:21 remaining. Archibald then missed the second of two free throws and the Bullets got even more incentive.

Parish swatted Ruland's shot into the stands, but Ballard was fouled by Archibald and made both free throws to make it 101-100 with 47 seconds left. A questionable out-of-bounds call let Boston retain possession, but then referee Jack Madden called an offensive foul on Parish, who was setting a screen for Bird, and the Bullets had one final chance.

"This was what we needed," Johnson said, still excited 20 minutes after his shot. "We felt all along we could beat these guys. But we knew we had to play 48 minutes. We've had a lot of chances to beat them this season and now that we have, the Celtics are going to have to think a little bit differently about us now."