It was Petty Officer Joseph R. Key, still in his hospital pajamas and waving his wounded hands, who asked today's central question as far as the Americans here are concerned.

"Why us? We're nothing, just a little base with no problems and good community relations," he said.

Key, 22, of El Paso, Tex., was one of two survivors who described for reporters the bloody terrorist attack on a Navy shuttle bus near San Juan Monday morning that left two persons dead and 10 wounded.

Armed Marines in flak jackets screened visitors, and security was tighter at all eight of the U.S. military facilities in Puerto Rico as he talked. Meanwhile, Puerto Rican politicians unanimously denounced the attacks, some using it to criticize both the U.S. government and the government of Puerto Rico.

The event is emerging as the latest in a series of violent punctuations marking Puerto Rico's slow movement toward resolving its relationship with the United States. But it was the worst incident here that anyone can remember.

"I usually drive [the bus], but this time I didn't," he said. It saved his life. A green truck cut in front of the yellow school bus, slowed twice and finally stopped near a white van. "The [bus] driver sat on the horn and at that point they started firing" from the van, he said. The 32-shot fusillade killed the driver, Petty Officer John R. Ball of Madison, Wis., and a radio man, Petty Officer Emil E. White of St. Thomas in the Virgin Islands. Everyone else hit the floor.

"It felt like a lifetime," said Chief Petty Officer Warren C. Smith, 39, of the time he spent waiting for the gun-fire to stop. When it did, he and Key pulled the driver's body from the seat, and then Smith turned the bus around and drove back to the Sabana Seca Communications base residential area. All five women aboard had been wounded, and one was moaning, "please don't hurt me anymore," he said.

Smith didn't know he had been wounded in the back and head by metal fragments, until the more seriously hurt had been cared for. His commander, Rear Adm. Arthur K. Knoizen, today called Smith a hero.

Of the 10 wounded, two remained in serious condition, and three more are considered fair to good. The others, including Key and Smith, were treated and released. Six other persons taking the bus to work Monday morning were not hurt in the incident.

Ball's widow, Patty, and her two children flew back to Madison, Wis., today to be with Ball's family. The other 700 military and civilian personnel at Sabana Seca, which is about 10 miles west of San Juan, were "in a state of shock . . . passive and solemn," according to their base commander, Cmdr. Michael Werner, but life returned to a grim normalcy today. c

"I told them not to react in terror . . . but rather to react in anger," Werner said of a general meeting Monday. School children rode buses under armed guards this morning, and a three-van convoy took techinicians to work along the same route as yesterday's attack.

Other security measures were secret. "Of course we're concerned there'll be more incidents," Knoizen told a news briefing. "But if they think they are going to drive us out of Vieques with acts like this, they better think again."

A communique left in a bus station telephone booth claimed the attack was the work of three small pro-independence groups, partly in retaliation for the death three weeks ago of a man jailed for protesting U.S. use of the island of Vieques for target practice. Angel Rodriquez Cristobal, a Puerto Rican Socialist Party member, was found hanged in his Tallahassee, Fla., jail cell Nov. 11.

Bomb targets on Vieques are an essential part of the massive training facilities that make the Roosevelt Roads base the Navy's largest anywhere in the world, Knoizen said, "Demonstrations are one thing . . . but this time they went one hell of a step too far," he said.

The groups who signed the communique were the same as those who claimed responsibility for bombings in Chicago and Puerto Rico in October, the Boricua Popular Resistance, and the Volunteers of the Puerto Rican Revolution. The AFPR also claimed responsibility for a fire-bombing at the La Hacienda bar near Sabana Seca on Oct. 5, where many off-duty Americans go to relax.

Knoizen praised Puerto Rican Gov, Carlos Romero Barcelo and local authorities for helping the FBI probe the incident. Romero was joined by most local politicans act" deserving repudiation by all islanders. However, Puerto Rican Socialist Party President Carlos Gallisa said the U.S. government's "continual abuse . . . of the people of Vieques" had provoked the attack.

Similarly, two members of Romero's party complained that those who "have dedicated themselves to attacking our government, trying to weaken our position of firmness towards the terrorists" were "just as guilty."

Rafael Hernandez Colon, chief of the Popular Democratic Party and Romero's principal opponent, responded that no one should try to make political capital out of the tragedy at Sabana Seca. Hernandez' party advocates a stronger form of the island's current commonwealth status, while Romero is a strong backer of statehood.