PHILADELPHIA (AP) _ A man police say terrorized his neighborhood with bomb threats for three years and painted swastikas on politicians' offices was caught after allegedly making a suspicious call to a state senator.

Michael Gaither, 39, is accused of leaving pipe bombs outside businesses and sending police a letter threatening to harm children if he didn't receive $15,000 as retribution for U.S. atrocities after World War II. The pipe bombs were never detonated.

``Who knows what's in these people's heads?'' Sgt. Michael O'Donnell replied when asked about a motive.

Police zeroed in on Gaither on Wednesday as he walked away from a pay phone. He was arrested after a brief foot chase.

He was arraigned Friday on more than 100 counts for crimes dating back to 1994, including arson, ethnic intimidation and causing a catastrophe.

Police believe the arrest solves vandalism attacks at the offices of U.S. Rep. Robert Borski and state Sen. Henry Salvatore. Vandals hit Borski's office in northeast Philadelphia at least three times between March and August 1996, scribbling swastikas and the words: ``U.S. Out,'' in black marker, smashing the front door and a window.

Police stepped up their efforts after receiving the threatening letter Nov. 17.

Investigators traced phone calls to a few pay phones in one neighborhood and began staking out phone booths. On Wednesday, someone called Salvatore's office and claimed responsibility for a vandalism incident last year.

Investigators wouldn't say how they linked Gaither to the other incidents.

Gaither, who lives with his mother and is apparently unemployed, has no criminal record and was not a suspect before his arrest, O'Donnell said.

Salvatore's aides said the Republican's sponsorship of an anti-ethnic-intimidation bill in 1982 could have motivated the vandalism. Aides to Borski, a Democrat, said they had no idea what motivated vandalism at his office.