Everyone knows suspicious neighbors. But when a Penn student pumped a dozen pistol rounds into his neighbors' apartment door - shooting off its lock and later telling police he thought they were Indian spies - he took neighborhood nosiness to extremes yesterday.

Police said the University of Pennsylvania law student, whom they declined to identify pending his arraignment on charges of aggravated assault and other offenses, lived in the same West Philadelphia building as the victims, two graduate students from India studying biomedical engineering at Drexel University.

"It's a bizarre case. You have people who are all in higher education, and you would think they would be open-minded . . . and accepting of each other's cultures. But something triggered in this guy's mind that [the neighbors] were not here for the right reasons," Lt. John Walker said.

Walker said the Penn student, a Korean American, accosted the Drexel students yesterday morning as all were leaving the building, a faded-glory, three-story, red-brick Victorian at 44th and Pine Streets.

When the Drexel students told the Penn student that they planned to return to India after their studies, the Penn student accused them of being spies, Walker said.

"The Drexel students figured he was a little crazy," and all went their separate ways to class, Walker said.

But around noon, the Penn student "decided to engage in more conversation" and banged on the Drexel students' door, Walker said. When he got no answer, he got his 9mm Glock handgun and emptied it into the lock, police said. Then he stepped inside, looked around, and left the building. Unbeknownst to the assailant, one of the Drexel students was cringing in his bedroom about 25 feet from the door.

Responding to reports of a burglary in progress, police sent squad cars to the building. They found slugs in the furniture and kitchen cabinets - in a city where gun violence has become epidemic.

When the Penn student returned, police were still there and the building was ringed with crime-scene tape. Police refused to let him enter. When he put up a fuss, they took him in for questioning, and the story came out.

Contact staff writer Michael Matza at 215 854 2541, or mmatza@phillynews.com.