Justin Nagtalon made mistakes. But he swears he saw the light after getting caught leaving his mark on the world illegally in 2007.

"I did graffiti. I stopped. I realized, 'I'm 25. This is juvenile,' " recalled Nagtalon, a Philadelphia graphic designer and artist known as El Toro. "I did my community service. The system actually worked for me."

Since then, Nagtalon has drawn and painted his two-legged alter ego - a cartoonish, beanie-wearing bull also named El Toro - exclusively on stickers and canvases. Nagtalon, now 26, sells pieces at gallery shows for $200.

And yet, as I type, more than a dozen of the artist's paintings are being held hostage by the Philadelphia Police Department in one of the most unorthodox and creepy investigations I've ever seen. One of the city's most successful civil-rights lawyers calls the case "bizarre."

Around 3:20 p.m. June 19, uniformed officers entered the T&P Fine Art gallery near Ninth Street and Passyunk Avenue, where Nagtalon had a month-long show.

"I asked if I could help them," gallery manager Gina Tibbott told me. "They said they were here for El Toro's artwork."

Tibbott thought they had come for a piece Nagtalon painted on a fallen "2-hour parking" sign. The officers said they were investigating El Toro for graffiti and confiscated everything with a price tag.

"I asked if they needed any paperwork to do that," like a warrant, Tibbott recalled. "They said no."

Ninth District Officer James Quick did the talking. At the end of the raid, he left his name and number and an ominous message:

Tell El Toro to call me.

Cat and bull

Quick had been hunting Nagtalon for months, but the artist had no idea the person behind the cat-and-bull game was a cop. In e-mails and on the photo-sharing Web site Flickr, Quick does not use his real name, title, or affiliation. He calls himself "The Police!!" and writes from an AOL account.

In February, The Police!! posted photos of Nagtalon with mocking messages. The artist was stumped.

"It could have been a cop. It could have been a 13-year-old I met at an art show," he said. "Whoever it was spooked the hell out of me."

Nagtalon blocked The Police!!, but Quick created another online account to stalk his prey.

"We've pieced the puzzle together. Now it's a matter of who we are going to make an example out of."

The note ended with :)

How low can you go?

After the raid, Quick ramped up his taunting. "When I hear from you we'll talk about different ways how we can handle this," he e-mailed June 20. "The more you cooperate the less trouble for both of us. I hate doing paperwork."

That unsigned message came from PhilaPolice9th@aol.com. A police spokesman confirmed to me that Quick had written it, but it should be noted Quick did not identify himself or use city e-mail.