A 15-year-old Wheaton youth was arrested yesterday and charged with murdering a Montgomery County tax assessor whose body, which had been bound and gagged, was found Wednesday in his car in an underground parking lot.

Montgomery County police said the discovery in a wooded area in Wheaton of a wallet belonging to the victim, George E. Angerman Jr., led them to the arrest of the suspect.

The youth was identified as Paul Edward Wersick, of 12037 Veirs Mill Rd. Police said he was arrested at his home and charged as an adult.

The motive for Angerman's killing is believed to be robbery, according to Cpl. Phillip B. Caswell, a spokesman for the county police.

He said police have been unable to establish any connection between Angerman and the suspect, and added that Angerman was apparently selected at random as a target for the alleged robbery.

It was not immediately known how much money may have been taken from the assessor, but he seldom carried less than $30, according to Caswell.

Angerman's body was found Tuesday morning in the underground parking lot of the Unibank office building in Rockville, where the assessor's office is located.

Authorities said Angerman had been bound, gagged with a red handkerchief, and shot in the temple as he sat in the driver's seat of his Mercury Capri. The shooting apparently took place about 6 p.m. Monday, authorities said.

Although police said the shooting occurred in connection with a robbery, Caswell said he could not explain precisely what precipitated the firing of the shot.

The wallet that led to the arrest was found about noon Tuesday near Veirs Mill and Randolph roads, in a wooded-area used as a teen-ager hangout, police said. The wallet, a credit card, and a blank check bearing the victim's name were found by a county employe doing street maintenance.

After obtaining names of youths who used the hangout, Caswell said, records were searched to see if any had fingerprints on file.

Following a comparison of file fingerprints with prints taken from the crime scene, police obtained a warrant for Wersick's arrest. He was picked up at 4:45 p.m.

Police said he lived with his mother but gave few details about him.

Although the discovery of the youth's fingerprints in the files indicated he may have come to the attention of police previously, Caswell said he could not elaborate.