OAKLAND — Ivan Rabb walked through the back door of the Old Yeller Café N Market, where his mother works, and could barely digest the scene in front of him. More than 100 people — twice what the fire marshal would allow — crammed the room, waiting for one of the nation’s elite high school basketball players to announce his college decision.

“I’m going to the University of Cal Berkeley,” Rabb said, triggering a wave of cheers.

Rabb, a 6-foot-10 forward from Bishop O’Dowd High, actually made the announcement four minutes before his scheduled 7 p.m. news conference Monday.

“I lost track of time. I didn’t prepare anything because I wanted to speak from the heart,” he said. The reception included a contingent of Cal students, hoping they’d have reason to celebrate. “I didn’t realize there would be that many actual students from Cal here. It was crazy.

“I haven’t been this happy for a long time, to be honest.”

The second-happiest person in the Bay Area quite likely is second-year Cal coach Cuonzo Martin, who scored a major recruiting coup by beating Arizona for the consensus top-10 national prospect. Rabb also had been courted by the likes of Kentucky, Kansas and North Carolina, and said Kentucky continued to call his mother daily.

Rabb’s commitment cannot become official until the spring signing period begins Wednesday.

Rabb said Martin called him for the first time within two or three days of getting the Cal job at this time last year and impressed him with honesty and determination.

“Everything he said sounded so sincere. I’m a person who gets vibes from people,” Rabb said. “Coach Martin brought so much energy, so much hunger to the campus.”

Recruiting expert Josh Gershon of Scout.com said recently that Rabb would be a significant recruiting piece for the Bears, if they could close the deal.

“From the buzz perspective, it’s a really big deal,” Gershon said. “If Cuonzo Martin wants to ultimately have success at Cal, he’s got to keep those local kids home, and that’s not something that’s happened in recent years.”

Rabb said he has no idea whether he will be a one-and-done to the NBA or might stay four years at Cal. He said his immediate goal is to help the Bears “go deep in the (NCAA) tournament” next season.

O’Dowd coach Lou Richie believes the transition to the college game will go well for Rabb.

“He’ll be very successful. He’s coachable, he wants to be good, he plays hard — he’s a coach’s dream,” Richie said. “The biggest challenge for him is putting on muscle. He needs to enjoy living in the weight room. Aside from that, everything will take care of itself.”

Rabb acknowledged he went back and forth on Cal and Arizona for weeks after shortening his list of schools. He finally made up his mind late Friday night.

After making his decision public, Rabb said his next piece of business was to resume twisting the arm of Georgia small forward Jaylen Brown, the nation’s No. 1 overall prospect, according to Scout. Rabb said he planned to call Brown on Monday night and try convincing him to come to Berkeley.

Still uncertain for Cal is the status of All-Pac-12 point guard Tyrone Wallace, weighing a possible a jump to the NBA. Either way, Rabb likes the team he’s joining, and welcomes a scenario where Cal fans will have high expectations.

“I will feel some pressure, but it’s all good for me. It’s what I’ve signed up for,” he said. “I know if I go in the bust my butt every day, I can’t be anything but successful.”