Bizarre and threatening letters taped to the door of a San Francisco synagogue Monday are being investigated as a hate crime even though police suspect they are the work of a transient with no particular hostility toward Jews.

An envelope taped to the door of Magain David Sephardim Congregation contained two rambling letters. One contained a threat that the writer would show up with a weapon.

Investigator Milanda Moore of the San Francisco Police Department said the suspected writer is Philip Baptista, a 51-year-old white man who recently returned to the United States from China.

"Every once in a while…he does these letter-writing campaigns," Moore said. "The problem is they unnerve a lot of people."

The incident occurred amid an outbreak of anti-Semitic attacks in Sacramento and Chicago.

In the past, Baptista has written letters to San Francisco District Attorney Terence Hallinan and to the Archdiocese of San Francisco, Moore said. He has also scrawled paint on the archdiocese and other public property.

He has two outstanding warrants for acts of vandalism. "He's the type who will do things to get attention," Moore said.

Since Monday, two more letters have been taped to the door of Magain David Sephardim, an Orthodox synagogue located in the inner Richmond District. Moore said Baptista is suspected of writing those letters as well.

Typically, Baptista's letters are "long, long, long, long letters about his life not directed to anyone specifically, just to whoever would read it," Moore said.

The letters found at Magain David Sephardim, she said, contained ramblings about his wife, China — "everything he can imagine."

The police's focus right now, Moore said, is locating Baptista so he can be questioned. She does not believe he harbors hostility toward Jews but will not rule out the possibility until she talks to him about his motives.