More than $5,000 in cash was found scattered about the Amtrak train compartment where a gunman allegedly killed his sister and her baby during a three-day siege, Police Chief Frederick K. Heineman said yesterday.

The discovery was revealed as authorities pieced together information on Mario Evangelista Navas Villabona, 29, who was arraigned yesterday on two charges of first-degree murder and a charge of kidnaping his sister's 3 1/2-year-old daughter, who was freed unharmed.

Navas was being held in the Central Prison hospital at North Carolina's maximum-security prison under 24-hour guard, where he was undergoing treatment for an ulcer, attorney Thomas Loflin said.

Navas was escorted in handcuffs to his arraignment, at which told District Court Judge Stafford Bullock he needed a Spanish-speaking interpreter. One was provided.

Prosecutor Kurt Stakeman asked the judge to allow the maximum time to prepare for a preliminary hearing, which was set Oct. 27. "We are now trying to determine who the defendant is -- he has used several names -- and what his record is," Stakeman said.

Heineman said a search of the first-class sleeper car where the gunman held the hostages turned up the cash, mostly in $100 bills, but police could not explain the money's presence. Heineman said authorities believe Navas bought a car in Miami with $4,500 in cash before boarding the New York-bound Silver Star in Jacksonville, Fla., Thursday night.

According to federal prison records, Navas was convicted in New York City July 30, 1976, of conspiracy and possession with intent to deliver a narcotic. He was sentenced to 15 years and served time at three prisons before being paroled in November, 1980, on condition that he return to Colombia.