The second suspect in the beating of a U.S. Park Police officer was arrested yesterday in Mobile, Ala., by FBI agents who learned he was on a Greyhound bus en route to Houston, authorities said.

Jose B. Salamanca, 38, did not resist when federal agents boarded the bus at midafternoon yesterday and identified themselves. He was carrying a small blue athletic bag and initially identified himself as Jose Torres, said Charles Spaht, an FBI agent in Mobile.

Salamanca, whose 35-year-old brother, Hector, was arrested Monday, is scheduled to appear before a magistrate in Mobile today. A second hearing will take place either today or tomorrow. Hector Salamanca has been charged with assaulting a federal officer while armed.

The severe beating of Officer James P. Culver, 24, produced an intensive investigation by the Park Police. The assault left Culver with multiple fractures, bruises to the brain and a fractured jaw.

Earlier yesterday, Maryland park police found Jose Salamanca's four-door Isuzu Trooper in Adelphi shortly after midnight.

At some point, U.S. Park Police also learned he was en route to Houston and passed the information to the FBI.

Federal agents were posted both in Mobile and Houston. Authorities said the two men have relatives in Houston. The brothers are from El Salvador, and immigration officials -- who also took part in the investigation -- yesterday said Hector Salamanca is in the country illegally. Jose Salamanca is a resident alien who was carrying his identification card yesterday, enabling the federal agents to identify him.

Police still have no motive for the beating. Court documents prepared for Hector Salamanca's arraignment alleged that the two brothers and a woman were drinking in Rock Creek Park when Culver approached them about 11:30 p.m. Sunday.

Culver, who was assigned to patrol the park, came upon the three at a parking lot in Grove 13. He apparently asked the two for identification. A driver's license for Jose Salamanca and an identification card for Hector Salamanca were found at the scene.

Hector Salamanca told investigators that he left the park while his brother and Culver were talking or arguing. Later, after Hector Salamanca returned to his apartment in the 1400 block of Tuckerman Street NW, he told police, he received a call from Jose saying he had a "problem with the police."

U.S. Park Police Chief Lynn Herring visited Culver at Washington Hospital Center yesterday, where a spokeswoman said he was improving but was still listed in critical condition. Officials said it may be some time before investigators can question Culver in detail.